Rainer Siegele

Ion beams for materials analysis

The contents of this book are: Concepts and Principles of Ion Beam Analysis; Overview of Techniques and Equipment; High Energy Ion Scattering Spectrometry; Nuclear Reactions. Ion Induced X-Ray Emission; Channeling; Depth Profiling of Surface Layers During Ion Bombardment; Low Energy Ion Scattering from Surfaces and Interfaces; Microprobe Analysis; and Critical Assessment of Analysis Capabilities.

Studies on spatial distribution of nickel in leaves and stems of the metal hyperaccumulator Stackhousia tryonii using nuclear microprobe (micro-PIXE)and EDXS techniques

Stackhousia tryonii Bailey is one of the three nickel hyperaccumulators reported from Australia. It is a rare, herbaceous plant that accumulates (Ni) both in leaf and stem tissues. Localisation of Ni in leaf and stem tissues of S. tryonii was studied using two micro-analytical techniques, energy dispersive X-ray spectrometry (EDXS) and micro-proton-induced X-ray emission spectrometry (micro-PIXE). Dimethylglyoxime complexation of Ni was also visualised by bright- and dark-field microscopy, but this technique was considered to create artefacts in the distribution of Ni. Energy dispersive X-ray spectrometric analysis indicated that guard cells possessed a lower Ni concentration than epidermal cells, and that epidermal cells and vascular tissue contained higher levels of Ni than mesophyll, as reported for other Ni hyperaccumulators. The highest Ni concentration was recorded (PIXE quantitative point analysis) in the epidermal cells and vascular tissue (5400 μg g-1 DW), approximately double that recorded in palisade cells (2500 μg g-1 DW). However, concentrations were variable within these tissues, explaining, in part, the similarity between average Ni concentrations of these tissues (as estimated by region selection mode). Stem tissues showed a similar distribution pattern as leaves, with relatively low Ni concentration in the pith (central) region. The majority of Ni (73-85% for leaves; 80-92% for stem) was extracted from freeze-dried sections by water extraction, suggesting that this metal is present in a highly soluble and mobile form in the leaf and stem tissues of S. tryonii.

The ANSTO high energy heavy ion microprobe

Recently the construction of the ANSTO High Energy Heavy Ion Microprobe (HIMP) at the 10 MV ANTARES tandem accelerator has been completed. The high energy heavy ion microprobe focuses not only light ions at energies of 2–3 MeV, but is also capable of focusing heavy ions at high energies with ME/q2 values up to 150 MeV amu and greater. First performance tests and results are reported here.

Long-term accuracy and precision of PIXE and PIGE measurements for thin and thick sample analyses

This paper describes PIXE/PIGE measurements on thin Micromatter Standard (±5%) foils run over a period of 10 years. The selected foils were typically 50 μg/cm2 thick and covered the commonly used PIXE X-ray energy range 1.4–20 keV and the light elements F and Na for PIGE studies. For the thousands of thick obsidian and pottery samples analysed over a 6-year period, the Ohio Red Clay standard has been used for both PIXE and PIGE calibration of a range of elements from Li to Rb. For PIXE, the long-term accuracy could be as low as ±1.6% for major elements with precision ranging from ±5% to ±10% depending on the elemental concentration. For PIGE, accuracies were around ±5% with precision ranging from ±5% in thick samples to ±15% in thin samples or for low yield γ-ray production.

The use of spectroscopic imaging and mapping techniques in the characterisation and study of DLD-1 cell spheroid tumour models

Determining the chemical and biological compositions of the tumour models used in pharmacological studies is crucial for understanding the interactions between the drug molecules and the tumour micro-environment. Conventional techniques for spheroid characterisation require intensive chemical pre-treatments that result in the removal of unbound metabolites. In this study, the spectroscopic techniques, scanning transmission ion microscopy (STIM), proton-induced X-ray emission (PIXE) mapping, scanning X-ray fluorescence microscopy (SXFM), and Fourier transform infrared (FT-IR) imaging were employed to gain complementary information on the compositions of untreated DLD-l cancer cell spheroids. When used together, these techniques exhibited great potential for providing a comprehensive over-view of the density, biochemistry and elemental compositions within the different regions of the spheroids. STIM density and elemental maps correlated well with cellular density across the spheroid, and showed the accumulation of S, Cu and various lighter elements in the necrotic region. High levels of oxidative stress were evident in the hypoxic region, and different degrees of cellular necrosis as well as high levels of lactate and collagen within the necrotic region were suggested by FT-IR markers. FT-IR imaging was further employed to study the pharmacodynamics of known the cytotoxins, cisplatin and Pt1C3. Cisplatin was observed to induce minimal biochemical changes to the spheroids following 24 hour incubations, whereas Pt1C3 caused severe cellular damage to the spheroid periphery; consistent with their different modes of action.

A Cylindrical Silicon-on-Insulator Microdosimeter: Charge Collection Characteristics

A novel silicon-on-insulator microdosimeter for estimating the radiobiological effectiveness (RBE) of a mixed radiation field is presented. An ion beam induced charge collection study has confirmed the microdosimeter possesses well defined micron sized 3D cylindrical sensitive volumes. An array of these SVs has the capability of studying the track structure of high energy heavy ions typical of a deep space environment.

Manganese profiles in freshwater mussel shells

Abstract The heavy ion microprobe in combination with particle-induced X-ray emission was used to measure the distribution of manganese in freshwater mussel shells ( Hyridella depressa ) from the Nepean river in south-eastern Australia. Close to the ventral edge, bands with an elevated manganese content have been detected. These are correlated with growth bands in the mussels containing increased amounts of organic material, relative to the calcium carbonate matrix. Calcium minima, which were correlated to the annual growth rings, were measured close to the umbo region of the shells.

LET dependence of the charge collection efficiency of silicon microdosimeters

A heavy ion microprobe was used to conduct ion beam induced charge (IBIC) collection imaging of silicon microdosimeters. The GEANT4 Monte Carlo toolkit was used to simulate these measurements to calculate ion energy loss in the device overlayer and energy deposition in the device sensitive volume. A comparison between experimental and theoretical results facilitated the calculation of charge collection efficiency profiles for several ions.

Ion beam induced charge characterisation of a silicon microdosimeter using a heavy ion microprobe

An ion beam induced charge (IBIC) facility has been added to the existing capabilities of the ANSTO heavy ion microprobe and the results of the first measurements are presented. Silicon on insulator (SOI) diode arrays with microscopic junction sizes have recently been proposed as microdosimeters for hadron therapy. A 20 MeV carbon beam was used to perform IBIC imaging of a 10 μm thick SOI device.

Mechanisms of murine cerebral malaria: Multimodal imaging of altered cerebral metabolism and protein oxidation at hemorrhage sites

Multimodal spectroscopic imaging resolved controversies on biochemical changes associated with cerebral malaria pathology. Using a multimodal biospectroscopic approach, we settle several long-standing controversies over the molecular mechanisms that lead to brain damage in cerebral malaria, which is a major health concern in developing countries because of high levels of mortality and permanent brain damage. Our results provide the first conclusive evidence that important components of the pathology of cerebral malaria include peroxidative stress and protein oxidation within cerebellar gray matter, which are colocalized with elevated nonheme iron at the site of microhemorrhage. Such information could not be obtained previously from routine imaging methods, such as electron microscopy, fluorescence, and optical microscopy in combination with immunocytochemistry, or from bulk assays, where the level of spatial information is restricted to the minimum size of tissue that can be dissected. We describe the novel combination of chemical probe–free, multimodal imaging to quantify molecular markers of disturbed energy metabolism and peroxidative stress, which were used to provide new insights into understanding the pathogenesis of cerebral malaria. In addition to these mechanistic insights, the approach described acts as a template for the future use of multimodal biospectroscopy for understanding the molecular processes involved in a range of clinically important acute and chronic (neurodegenerative) brain diseases to improve treatment strategies.