Klas Malmqvist

Accumulation of calcium and loss of potassium in the hippocampus following transient cerebral ischemia: a proton microprobe study

This study explored (a) whether postischemic accumulation of calcium in hippocampal neurons precedes or occurs pari passu with light microscopical signs of delayed neuronal necrosis, and (b) whether calcium initially accumulates in dendritic domains, presumed to have a high density of agonist-operated calcium channels. Transient ischemia of 10-min duration was induced in rats, and the animals were studied after 1, 2, 3, and 4 days of recovery. We measured total calcium and potassium contents in the stratum oriens, pyramidale, radiatum, and moleculare of the CA1 and CA3 sectors, using particle induced x-ray emission (PIXE) in the proton microprobe mode. The results showed significant accumulation of calcium and loss of potassium after 3 and 4 days of recovery in the CA1 sector, which developed neuronal necrosis, but not in the CA3 sector, which showed only occasional damage. In a few animals, calcium accumulation (and loss of potassium) was observed with no or only mild visible damage, but in the majority of animals the accumulation of calcium correlated to signs of neuronal necrosis. Since calcium accumulation was similar in all strata examined, the results failed to reveal preferential accumulation in dendritic or somal regions. Based on our results and those of Dux et al., we emphasize the possibility that delayed neuronal death is, at least in part, caused by increased calcium cycling of plasma membranes and gradual calcium overload of mitochondria.

Elimination of Charging in the Proton-Induced X-Ray Emission Analysis of Insulating Samples

Anomalous background due to charging in the proton-induced X-ray analysis of insulators is eliminated by inserting a heated carbon filament or by raising the pressure in the sample chamber.

Proton and Electron Microprobe Analysis of Human Skin

Abstract In order to demonstrate the feasibility of the proton microprobe in the analysis of dermatological material when a spatial resolution of a few micrometres is sufficient and to compare it with the electron microprobe technique, duplicate sections of human skin have been analysed with both methods. A skin sample was obtained from each of three healthy volunteers. After cryosectioning (12 μm) and freeze-drying adjacent sections of each sample were scanned by the electron microprobe and the proton microprobe, respectively.

Dedicated accelerator and microprobe line

Abstract The development of a dedicated facility for nuclear microprobe analysis and the experiences from using it are discussed. The general properties of the present Lund nuclear microprobe will be described and the advantages of using a dedicated accelerator discussed.

A highly sensitive method for rare-earth element analysis using ionoluminescence combined with PIXE

Abstract In Ion Beam Analysis (IBA), a beam of energetic particles (a few MeV/amu) is normally employed. Particle induced X-ray emission (PIXE) is one of the well-established IBA methods for accurate element analysis with the capabilities of a low detection limits and the absolute quantification for many elements. Nevertheless, for intermediate elements, including rare-earth elements (REEs), the experimental detection limits of PIXE in analysis of some geological materials are too high. The IonoLuminescence (IL) method is a sensitive analytical method for REE analysis based on the facts that the luminescence emission lines for REEs are characterised by narrow peak, stable position and high yields in a variety of minerals. Thus, similar to PhotoLuminescence (PL) and CathodoLuminescence (CL), the IL can be employed as a sensitive method for REE study. In the present work, synthetic minerals such as zircon and calcite separately doped various single REE were studied by combined IL and PIXE. An apatite standard sample containing several REEs was also investigated. The IL detection limits of most REE elements involved were estimated much lower than those offered by PIXE.

Imaging with ionoluminescence (IL) in a nuclear microprobe

Abstract A system for the detection of luminescence induced by a 2.5 MeV proton beam (ionoluminescence; IL) to be used in combination with a nuclear microprobe is described. Results of IL imaging are compared with X-ray and secondary electron maps acquired simultaneously. Beam damage is investigated by panchromatic IL imaging and IL yield decay. An IL wavelength dispersive study has also been done with the presently rather simple system. Limitations of the IL technique as well as development plans for an upgraded IL analytical facility are discussed.

Calibration and long-term stability of a PIXE set-up

A general mass calibration procedure of a PIXE set-up is described. As an example, the results of the calibration of the PIXE set-up in Lund are given. For the calibration commercially available standards were used. The parameters of a physical model were adjusted to fit a calibration curve. To decrease errors due to inhomogeneities of the standard foils, the average from four different pieces of each foil was taken. The accuracy of the calibrated system in Lund is estimated to be better than 5% for individual elements and still less for ratios of adjacent elements. For long-term quality control of the results, a special sample has been designed. This consists of a thick silver plate with a small copper spot in the centre. It is very sensitive to small changes in a PIXE set-up. By analysing this sample periodically, mistakes in the arrangement are promptly detected-a feature which is much appreciated in a mixed research, development and routine analysis laboratory. Also a measure of the long-term stability is obtained. For the Lund system, the long-term stability is 2.5% for a homogeneous sample and 4% for a small (inhomogeneous) sample.

PIXE and ionoluminescence — A synergetic analytical combination

The purpose of this paper is to demonstrate that ionoluminescence and PIXE are genuinely complementary techniques and that the combination represents a powerful analytical tool, particularly in geochemistry. Ionoluminescence can be used for imaging and qualitative analysis of elements and chemical compounds. The quantification of ionoluminescence data, however, requires an improved understanding of luminescence physics. The trace element properties of PIXE may be of major importance in this development.

Comparison between PIXE and XRF for applications in art and archaeology

Abstract The properties of X-ray fluorescence and particle-induced X-ray emission have been compared with special reference to applications within art and archaeology. The two techniques have each been found to have several specific merits useful in the analysis of various objects in these fields. Together they offer the museum scientist and archaeologist excellent complementary analytical tools for nondestructive multielemental analysis.

Determination of local areal densities of heterogeneous biological samples by elastically backscattered protons in pixe microanalysis

Abstract It is shown that by using elastically backscattered protons as a measure of the areal mass density of the sample, a quantitative determination of element concentrations in biological material by PIXE can be achieved. To improve the accuracy in the local areal mass density determination, the backscattering yield is calibrated for different matrix compositions and a correction for changes in scattering cross sections is suggested.