W.J. Teesdale

Copper, iron and zinc in Alzheimer's disease senile plaques

Concentrations of copper (Cu), iron (Fe) and zinc (Zn) were measured in the rims and cores of senile plaques (SP) and in the neuropil of the amygdala of nine Alzheimers disease (AD) patients and in the neuropil of the amygdala of five neurologically normal control subjects using micro particle-induced X-ray emission (micro-PIXE). Comparison of SP rim and core values revealed no significant differences between levels of Cu, Fe or Zn. Zinc and Fe in SP rims and cores were significantly elevated in AD compared with AD neuropil (P<0.05). Copper was significantly elevated (P<0.05) in the rim of SP compared with AD neuropil. Comparison of AD and control neuropil revealed a significant (P<0.05) elevation of Zn in AD subjects. The elevation of these elements in SP in AD is of interest in light of the observation that Cu, Fe and particularly Zn, can accelerate aggregation of amyloid beta peptide.

Quantitative PIXE microanalysis of thick specimens

Abstract Methods of standardization in quantitative micro-PIXE analysis are reviewed and various issues that bear on analytical accuracy are explored; pertinent recent work on Si(Li) X-ray detector response is included and some geochemical examples are drawn upon. Extension of the GUPIX software to deal with multilayer targets, including secondary fluorescence within and between layers, is reported; analytical examples include alloy foils and multilayer solar cell structures.

Oscillatory zinc distribution in Arctic char (Salvelinus alpinus) otoliths:: The result of biology or environment?

Scanning proton microprobe (SPM) analysis and imaging was used to map the distribution of zinc in otoliths of anadromous and non-anadromous Arctic char (Salvelinus alpinus) from the Canadian Arctic. Zinc distribution patterns were oscillatory with concentrations ranging from 35 to 240 ppm. Superimposition of the zinc distribution on optical images of the otoliths permitted correlation of zinc uptake with annular structure in the otoliths and with strontium patterns from the same otolith. Well defined oscillations of zinc concentrations were observed in the otoliths, particularly in the first few years in all samples. In anadromous fish, these overlapped with the onset of the strontium oscillations that were indicative of anadromy and then declined; in non-anadromous fish the oscillations generally continued to later years. Oscillatory zoning of zinc may indicate: (1) variations in the concentration of zinc in water; (2) variations in nutrient availability in the environment; (3) temperature variations in the habitat occupied; or (4) a combination of zinc concentration, nutrient availability or temperature changes. As such, the systematic distribution of zinc in otoliths has the potential to provide temporally constrained information on fish habitat and/or fish biology.

Scanning proton microprobe analysis of strontium in an arctic charr, Salvelinus alpinus, otolith: implications for the interpretation of anadromy

SynopsisScanning proton microprobe imaging has been used to map the distribution of strontium (Sr) in an arctic charr, Salvelinus alpinus, otolith. X-ray maps show that Sr variation follows an oscillatory zoned pattern which correlates with optically resolved zones (annuli). The internal region of the otolith shows optical zonation but no significant Sr content. Comparison of the optical image with the Sr X-ray map provides evidence of when the fish entered a high Sr environment. This may be interpreted as when the fish migrated from fresh water to a marine environment; this particular fish first migrated to sea in its eighth year. Micro-PIXE point analysis was used to determine the abundance of Sr in annuli along a radius from the nucleus to an outer edge; Sr levels in the internal region were about 10 ppm and variation in the outer zoned region was between 62 and 175 ppm. Detection limits for Sr are in the 1–2 ppm range. Other trace elements, such as transition elements, were found to be present in some growth regions in the 1–20 ppm range. Proton beam analysis is a non-destructive analytical technique capable of preserving the spatial integrity of trace-element data in otoliths such that element distribution may be linked to the growth structure of the otolith.

Analytic fitting of monoenergetic peaks from Si(Li) X-ray spectrometers

Abstract Monoenergetic X-ray lines produced by diffraction from a curved crystal monochromator have been used to test the applicability of the Hypermet function for Si(Li) detectors. Excellent fits are achieved; the functions parameters vary smoothly with energy, and the intensity of the non-Gaussian peak components correlates with the thickness of the frontal dead layer where charge collection is incomplete. Accurate silicon escape peak intensities are presented and the contribution to the lineshape from Compton-scattered events is discussed qualitatively.

Micro-PIXE as a complement to electron probe microanalysis in mineralogy☆

Abstract Standardization methods and limits of detection for the analogous techniques of micro-PIXE and electron-probe microanalysis (EPMA) are compared in the context of mineralogical applications, specifically in the analysis of sulfide and oxide minerals. Micro-PIXE benefits by adopting and adapting techniques from EPMA and the two techniques are often deployed in tandem to provide a full characterization spanning major, minor and trace elements. Various examples are given of work in progress.

Deviation of the Kβ /Kα intensity ratio from theory observed in proton-induced X-ray spectra in the 22⩽Z⩽32 region

Measurements of I(K beta )/I(K alpha ) for proton-induced X-rays from thin targets in the 22<or=Z<or=32 region confirm a previously suspected systematic discrepancy between experimental data and the theoretical predictions for de-excitation of a single K vacancy in a neutral atom. The present paper is the first proton work to pay specific attention to the KMM radiative Auger satellite and to use a measured resolution function in unfolding K alpha -K beta peak overlaps. A discrepancy is common to electron-, photon- and proton-induced ionisation but sufficient precision is not yet available to reveal any small differences among the three processes, which might arise from differing multiple ionisation.

Cultural sediment analyses and transitions in early fishing activity at Langenesværet, Vesterålen, Northern Norway

The development of specialized and commercial fishing activity in the island archipelago of Lofoten and Vesteralen in northern Norway is a critical foundation from which to understand the subsequent spread of commercial fishing across the north Atlantic region during the medieval and early modern period. One little understood aspect of this development is the relationship between medieval commercial fishing stations (fiskevaer) and earlier fishing activity. In this article, cultural sediment deposits at Langenesvaeret, Vesteralen, Northern Norway provide an opportunity to examine this relationship and its implications for current historical models of fishing development in northern Norway and the north Atlantic region. Conventional and AMS radiocarbon dating techniques are used to establish a chronology for the deposits, while activities associated with the sediments are characterized using thin-section micromorphology supported by proton induced X-ray emission spectrometry (PIXE). The results suggest that the site commenced formation as early as ca. 3000 B.C. and that the site was first used for specialized fishing activity from the early centuries A.D. The medieval commercial fiskevaer settlement at Langenesvaeret was introduced to an area that had a longstanding tradition of specialised fishing activity.

MICRO-PIXE STUDIES OF SR ZONING IN ARCTIC CHARR OTOLITHS : MIGRATORY BEHAVIOUR AND STOCK DISCRIMINATION

Abstract Micro-PIXE has been used to determine the content of strontium in the growth zones of Arctic charr otoliths. A well-defined correspondence is observed between the optically observed growth zones and the strontium zoning pattern. Line-scan data indicate whether or not the fish concerned is anadromous, and they define the years in which migration to the sea has taken place; they also are sensitive to the geographic origin of the fish. These results suggest that micro-PIXE can be a useful tool in the management and conservation of the Arctic charr.

Comparison of in-situ gold analyses in arsenian pyrite

Abstract In-situ analyses of Au in arsenian pyrite, a Au-carrier common in certain ores refractory to direct cyanidation, are feasible by proton and ion microprobe. These in-situ microbeam analysis techniques provide a better geochemical understanding of the distribution of Au in ore than traditional bulk chemical analyses. The practical minimum detection level (MDL) by particle induced X-ray excitation (PIXE) or proton microprobe (Micro-PIXE) is 21–26 ppmw for a beam density of 22–24 pA/μm 2 . A lower MDL of ∼400 ppbw was obtained by secondary ion mass spectrometry (SIMS) or ion microprobe. Results of analysis of the same grains by both methods are not readily comparable because of the inhomogeneous distribution of Au in arsenian pyrite and the different volumes analyzed (∼5000 μm 3 for PIXE vs ∼2400 μm 3 for SIMS). In addition, the geometry of the volume analyzed by each technique is different: a parallelepiped by Micro-PIXE and a thin disc by SIMS.