Femap Research Articles

Modeling soil moisture from in situ portable X-ray spectrometer measurements: A novel approach for correcting geochemical data across different environments and climatic conditions

The portable X-ray fluorescence (pXRF) spectrometer is widely employed for in situ analysis of both contaminated and uncontaminated soils. However, the accuracy of the measurements can be significantly affected by soil moisture, resulting in unreliable soil pollution monitoring. This effect has already been studied and quantified, but this is ineffective if the soil moisture in the field is unknown. Given the considerable variability of soil moisture conditions across time and space, significant bias during in situ investigations remains a main issue. This study introduces a novel method to estimate soil moisture directly from pXRF field measurements, enabling its reliable use in almost any field condition. The study was conducted using soil samples and in situ pXRF soil surface measurements in Estarreja (Portugal) and Vicdessos (France). In the first experiment, the innovative approach involved modeling soil moisture directly from the raw XRF measurement errors obtained in moist soils using multiple regression. In the second experiment, metal concentrations were modeled as an exponential function of the moisture content. The final model integrates both approaches to correct field data from geochemical mapping in diverse environments, including a coastal region in Portugal and a mountainous region in France. Our findings demonstrate that this simple, efficient and cost-effective method accurately predicts soil moisture (U) using pXRF, as shown by the equation Umeasured = 1.0028 x Uestimated (r2 = 0.9715). The model effectively corrected up to 70% of moisture-induced errors in metal concentrations in the wettest soils and produced more reliable soil Fe, Pb, and Zn maps. Specifically, the accuracy improvement was at least 32% in drier soils (Portugal) and at least 55% in wetter soils (France). This study offers a cost-effective, efficient solution for employing pXRF in geochemical mapping across different climatic conditions and soil environments.

Developing regional soil micronutrient management strategies through ensemble learning based digital soil mapping

Mapping of soil micronutrient variability is critical for improving agronomic biofortification. This study used 1778 surface soil samples collected from four agro-climatic regions of the Indo-Gangetic Plain of India to produce digital soil maps of available Zn, Cu, Fe, and Mn using 52 environmental covariates at a resolution of 150 m. The micronutrient prediction accuracy was compared for 14 machine learning approaches and their ensemble model. The hybrid ensemble model outperformed all 14 base learners and was subsequently used for producing micronutrient maps. All four micronutrients exhibited sufficient spatial variability. Both available Zn and Fe maps exhibited lower prediction uncertainties. Moreover, the inter-relationship between micronutrient concentration in soil and rice grain was explored to understand the Zn and Fe biofortification potential. The linear regression models revealed moderate agreement between soil available and grain micronutrient concentrations, with R2 values of 0.52–0.63 for Zn and Fe, respectively. The developed models were used to predict grain Zn and Fe content from their respective soil concentrations, indicating the potential of the tested approach to identify specific pockets where rice varieties with biofortification potential can be planted. In the future, the digital soil mapping approach tested herein can help policymakers with regional decision-making, encouraging nutrient-based subsidy and investment opportunities and sustainable micronutrient recommendations toward micronutrient-enriched food. Further research is needed to develop a digital soil intelligence platform using micronutrient DSM products in resource-poor countries.

The low ferric chelate reductase activity and high apoplastic pH in leaves cause iron deficiency chlorosis in ‘Huangguan’ pears grafted onto quince A grown in calcareous soil

Quince (Cydonia oblonga Mill.) is a dwarfing rootstock often used in pear cultivation. However, the pear cultivar ‘Huangguan’ (Pyrus bretschneideri Rehd. cv) grafted onto quince A (HG-QA) suffered iron (Fe) deficiency chlorosis in the calcareous soils of North China, while ‘Huangguan’ grafted onto Pyrus betulifolia (HG-PB) did not. We hypothesized that the higher leaf apoplastic pH of HG-QA than HG-PB causes Fe deficiency chlorosis by restricting Fe transportation within leaves. Three-year-old rootstocks quince A and Pyrus betulifolia and the combinations HG-QA and HG-PB were grown in the same orchard in a calcareous soil. Newly expanded leaves were analysed for Fe related properties. Micro X-ray fluorescence analysis was used for Fe mapping within the individual leaves. The extractable Fe(II) concentrations in quince A and HG-QA leaves were much lower than those in Pyrus betulifolia and HG-PB, even though the total leaf Fe concentrations were similar. More Fe was located near the leaf midrib in quince A and HG-QA than in Pyrus betulifolia and HG-PB. These were correlated with the lower ferric chelate reductase (FCR) activity in the chlorotic leaves of the quince A rootstock than Pyrus betulifolia and the lower FCR activity and higher apoplastic pH in the chlorotic leaves of the HG-QA rootstock-scion combination than HG-PB. In conclusion, the reduced Fe availability within the leaves caused by the lower FCR activity and higher apoplastic pH compared with those of HG-PB led to HG-QA leaf chlorosis in calcareous soils. This result implies that rootstocks are involved in the regulation of leaf Fe utilization by scions.

Multimodal synchrotron X-ray fluorescence imaging reveals elemental distribution in seeds and seedlings of the Zn-Cd-Ni hyperaccumulator Noccaea caerulescens.

The molecular biology and genetics of the Ni–Cd–Zn hyperaccumulator Noccaea caerulescens has been extensively studied, but no information is yet available on Ni and Zn redistribution and mobilization during seed germination. Due to the different physiological functions of these elements, and their associated transporter pathways, we expected differential tissue distribution and different modes of translocation of Ni and Zn during germination. This study used synchrotron X-ray fluorescence tomography techniques as well as planar elemental X-ray imaging to elucidate elemental (re)distribution at various stages of the germination process in contrasting accessions of N. caerulescens. The results show that Ni and Zn are both located primarily in the cotyledons of the emerging seedlings and Ni is highest in the ultramafic accessions (up to 0.15 wt%), whereas Zn is highest in the calamine accession (up to 600 μg g–1). The distribution of Ni and Zn in seeds was very similar, and neither element was translocated during germination. The Fe maps were especially useful to obtain spatial reference within the seeds, as it clearly marked the vasculature. This study shows how a multimodal combination of synchrotron techniques can be used to obtain powerful insights about the metal distribution in physically intact seeds and seedlings.

Seismic progressive collapse mitigation of buildingsusing cylindrical friction damper

The occurrence of progressive collapse induced by the removal of the vertical load-bearing element in the structure, because of fire or earthquake, has been a significant challenge between structural engineers. Progressive collapse is defined as the complete failure or failure of a part of the structure, initiating with a local rupture in a part of the building and can threaten the stability of the structure. In the current study, the behavior of the structures equipped with a cylindrical friction damper, when the vertical load-bearing elements are eliminated, is considered in two cases: 1-The load-bearing element is removed under the gravity load, and 2-The load-bearing element is removed due to the earthquake lateral forces. In order to obtain a generalized result in the seismic case, 22 pair motions presented in FEMA p 695 are applied to the structures. The study has been conducted using the vertical push down analysis for the case (1), and the nonlinear time-history analysis for the second case using OpenSEES software for 5,10, and 15-story steel frames. Results indicate that, in the first case, the load coefficient, and accordingly the strength of the structure equipped with cylindrical friction dampers are increased considerably. Furthermore, the results from the second case demonstrate that the displacements, and consequently the forces imposed to the structure in the buildings equipped with the cylindrical friction damper substantially was reduced. An optimum slip load is defined in the friction dampers, which permits the damper to start its frictional damping from this threshold load. Therefore, the optimum slip load of the damper is calculated and discussed for both cases.

Automated static structural FEA environment in MATLAB using Solid Edge and Femap

Automated static structural FEA environment in MATLAB using Solid Edge and Femap

Design and Analysis of Connecting Rod Using Femap with Nx-Nastran

Design and Analysis of Connecting Rod Using Femap with Nx-Nastran

Global mapping of lunar refractory elements: multivariate regression vs. machine learning

Context.The quantitative estimation of elemental concentrations at the spatial resolution of hyperspectral near-infrared (NIR) images of the lunar surface is an important tool for understanding the processes relevant for the origin and evolution of the Moon.Aims.We aim to map the abundances of the elements Fe, Ca, and Mg at a typical accuracy of about 1 wt.% at the spatial resolution of the Moon Mineralogy Mapper (M3) instrument on-board Chandrayaan-1 lunar mission.Methods.The NIR reflectance of the lunar regolith is an integrated response to the presence of refractory elements and soil alteration processes. Our approach was to define a combination of spectral parameters that are robust with respect to the effects of soil maturity. We calibrated the spectral parameters with respect to elemental abundances measured by the Lunar Prospector Gamma Ray Spectrometer (LP GRS) and the Kaguya GRS (KGRS). For this purpose, we compared a classical multivariate linear regression (MLR) approach and the machine learning based support vector regression (SVR) technique applied to M3global observations.Results.The M3-based global elemental maps are consistent in distribution and range with the LP GRS and KGRS elemental maps and do not show artifacts in immature areas such as small fresh craters. The results derived using MLR and SVR are compared to sample-based ground truth data of the Apollo and Luna sample-return sites, where the root-mean-square deviations obtained by the two regression models are similar.Conclusions.The main advantage of the proposed new algorithm is its ability to minimize artifacts due to space-weathering effects. The elemental maps of Mg and Ca provide additional information and reveal structures not always visible in the Fe map. The global elemental abundance maps derived for the fully calibrated M3observations might thus serve as important tools to investigate the lunar geology and evolution.

Spatial distribution of Fe and Mn in paper mill effluent affected agricultural soils in Morigaon, Assam

The spatial distribution of heavy metals (Fe and Mn) in the paper mill contaminated area of Jagiroad, Assam, India were investigated using statistics, geostatistics and GIS techniques. The total concentration of Fe and Mn were determined for 188 samples collected from the contaminated area. The mean concentration of Fe (7629 mg kg1) was high. The highest and the lowest standard deviation were observed in the Fe (1749) and pH (0.81), respectively. Analysis of the isotropic variogram indicated that the Fe semivariogram was well described with the Gaussian model, with the distance of spatial dependence being 1354 m, while Mn was well described with the spherical model, with the distance of spatial dependence being 833 m. The ordinary kriging estimates of Fe and Mn maps showed that high concentrations of these metals occured in the low-lying areas like bils (lakes). For both the investigated heavy metals the prediction of goodness (G) value was greater than zero. This indicates that spatial prediction is better than assuming mean of observed value as the property value for any unsampled location. Thus the geostatistical method was spatial variability of Fe and Mn.

Post-crystallization alteration of natural uraninites: Implications for dating, tracing, and nuclear forensics

Abstract This study presents systematic chemical (U, Pb, Ca, Si, Fe) mapping coupled with in situ analyses of major, minor and trace elements, U/Pb, 207Pb/206Pb, and O isotopic compositions of natural uraninites (UO2) from two samples of the high-grade uranium ore from the Cigar Lake unconformity-related uranium deposit (Athabasca Basin, Saskatchewan, Canada). The studied uraninites are characterized by major chemical and isotopic heterogeneities expressed at small scale (µm to tens of µm), from almost pristine zones to strongly altered material. The 206Pb/238U and 207Pb/235U ratios of the different areas are widely spread and depict two similar and well-defined Discordia, providing an upper intercept age of crystallization at ca. 1300 Ma (1299 ± 4 and 1308 ± 14 Ma, respectively) and lower intercepts at 38 ± 13 and 72 ± 22 Ma, respectively. The freshest areas are characterized by sub-concordant 206Pb/238U and 207Pb/235U ratios, identical chemical compositions and similar very low δ18O values (−39.3 to −31.4‰). These data indicate that the two uraninites both crystallized at ca. 1300 Ma, from the same fluid and under identical physico-chemical conditions. Alteration is characterized by (i) the progressive incorporation of Ca, Si, and Fe, reaching several wt.%, which substitute to the radiogenic Pb and cause a progressive decrease in the Pb/U isotopic ratios. The radiogenic Pb is also substituted by water during the alteration, (ii) concomitant variations in trace element contents (As, Mn, V, LREEs, Sr, Th, B, Ba, Nb, for example) and (iii) heavier δ18O signatures (−22.5 to −8.91‰), typical of meteoric waters, in the altered zones. This combined approach demonstrates that fluid-driven post-crystallization exchanges affected each uraninite during recent fluid flow events (ca. 40 Ma and 70 Ma respectively). The relatively high dispersion of the Pb/U ratios in relation to the Discordia for both samples is considered as linked to a local (nm to µm-scale) differential mobility between lead and uranium within the uranium oxides. The chemical changes affecting elements previously considered as immobile in uraninite, such as REEs, indicate that these elements are not preserved during the post-crystallization alteration process studied here. Alteration processes may therefore have a major impact on the classical geochemical tracers, such as REE patterns or LREE/HREE ratios, currently used in nuclear forensic studies. The isotopic and chemical tracers currently used to track back the origin, age and history of natural uraninites should therefore be considered with a high degree of caution to avoid misleading and erroneous conclusions. Moreover, the comparison of calculated U-Th-Pb chemical, 207Pb/206Pb, and Pb/U isotopic ages shows that the use of age clustering for determining U-Th-Pb chemical ages and 206Pb/207Pb ages is not appropriate for constraining crystallization stage(s) of altered uraninites and for deciphering the different fluid events that potentially altered or recrystallized the uraninites over time. This study also indicates that estimation of the crystallization age of uraninite from substitution trends of Pb to Ca is not applicable to unconformity-related U deposits and results in overestimated ages because of an initial integration of calcium in the uraninite lattice at the time of crystallization.

The accumulation of Ni in serpentines and garnierites from the Falcondo Ni-laterite deposit (Dominican Republic) elucidated by means of μXAS

Ni-bearing serpentines and garnierites (Ni-bearing Mg-phyllosilicates) are the main Ni ores in the Falcondo Ni-laterite deposit (Dominican Republic). In the present paper a set of garnierite samples and the associated Ni-bearing serpentines with characteristic mineral compositions and textures, from the saprolite horizon, were studied by EMPA, μXRF and μXAS. The ultimate goal is to elucidate, for the first time, the Fe speciation and the Ni local environment of saprolite ores from Ni-laterites of the Dominican Republic. The chemical composition of the minerals has been obtained by means of EMPA and the Ni, Fe and Cr elemental maps obtained by μXRF allowed distinguishing the saprolite fragments containing Ni-bearing serpentines and Fe oxyhydroxides from the garnierite veins. The Fe K-edge μXANES demonstrated that Fe in the Ni-poor primary serpentine is mostly in the Fe2+ form, whereas in the Ni-bearing serpentine constituting the bulk of the saprolite and in the Fe-bearing garnierite Type I Fe was in the form of Fe3+. In parallel, the local environment of Ni determined by means of Ni K-edge μEXAFS confirmed that in Ni-poor primary serpentines Ni formed a homogeneous Ni–Mg solid solution, in garnierites formed Ni–Ni clusters, and in Ni-bearing secondary serpentines Ni was found in Ni–Mg and Ni–Ni mixed sites. This paper explains the accumulation of Ni, the speciation of Fe in garnierites with various mineral compositions and in Ni-bearing serpentines from the saprolite horizon in Ni-laterite deposits.

Changes in micro-fabric and re-distribution of Fe and Mn with nodule formation in a floodplain soil

Ferromanganese nodules are common features in aquic soils of the temperate climate. Although they are intensively studied due to their pedogenic significance, there is a lack of knowledge on the relationship between their micro-fabric and distribution of their major chemical components. Our aim was to fill this gap and to relate these characteristics to the different stages of the nodule development in the soil. To fulfill our aims, ferromanganese nodules from a gleyic fluvisol profile was separated in which nodules with strongly varying appearance and fabric are present in a wide depth interval, so they are expected to represent the different stages of nodule formation. Micro-chemical analyses were carried out on the polished surface of 28 nodules. Micro-X-ray fluorescence spectrometry was used to produce Fe and Mn elemental maps of the whole nodules as well as line scan analyses along perpendicular cross sections. Additionally, the spatial distribution and major element associations of Fe and Mn within the individual nodules were studied by point analyses at 775 spots by electron micro-probe analysis. Typic and concentric nodules in the soil exhibited both similar (presence of outer coating band) and different (undifferentiated and banded interiors, respectively) characteristics in their micro-fabric. These were related to the rate of hydromorphism in the soil which was found to determinate the major processes (accretion vs. impregnation) forming the fabric of the nodules. The following stages of the nodule development were distinguished: (1) cementation, (2) formation of outer band, (3) re-arrangement and slow impregnation of nodules’ interior, and (4) fast impregnation of the interior and exfoliation of outer band. We found that separation of Fe and Mn is characteristic of each stage of nodule formation. However, as long as spatial segregation occurs in the first stages, displacement of Mn by Fe is rather typical later. Fabric and appearance of nodules form by varying rate and dominance of accretion and impregnation relatively slowly. However, distribution pattern of Fe and Mn within the nodules may exhibit much faster changes simultaneously. Complex micro-chemical analyses support a powerful tool to follow such changes and to get a deeper insight into the genesis of ferromanganese nodules.

Bioavailability of nutrients in Australia from Mobile Metal Ion® analysis of catchment outlet sediment samples: continental-scale patterns and processes

Catchment outlet sediments (0–10 cm depth, sieved to <2 mm) collected at a very low density over most of the Australian continent have been analysed using the Mobile Metal Ion (MMI®) partial extraction technique. Of the 54 elements determined, eight are generally regarded as essential nutrients for plant growth: Ca, Cu, Fe, K, Mg, Mn, P and Zn. A further three, Mo, Ni and Se are considered significant micronutrients. Estimation of ‘bioavailability’ from MMI® analysis gives results comparable with standard agricultural measurements for many nutrients. Percentage ‘bioavailability’, operationally defined here as the ratio of MMI® concentration to total element concentration, has been investigated and ranges from 31% for Se to 0.1% for Fe. Smoothed (kriged) colour raster maps for continental Australia have been produced for these 11 nutrients and interpreted in terms of lithology (e.g. presence of carbonates in the MMI® Ca map), mineralization (e.g. known mineral districts in the Cu and Zn maps), environmental processes (e.g. salinity in K map, weathering and acid generation in Fe map) and agricultural practices (e.g. application of fertilizers in the MMI® P map). This first application of a partial extraction technique at the scale of a continent has yielded meaningful, coherent and interpretable results.

Imaging of stroke: a comparison between X-ray fluorescence and magnetic resonance imaging methods

A dual imaging approach, combining magnetic resonance imaging to localize lesions and synchrotron rapid scanning X-ray fluorescence (XRF) mapping to localize and quantify calcium, iron and zinc was used to examine one case of recent stroke with hemorrhage and two cases of ischemia 3 and 7 years before death with the latter showing superficial necrosis. In hemorrhagic lesions, more Fe is found accompanied with less Zn. In chronic ischemic lesions, Fe, Zn and Ca are lower indicating that these elements are removed as the normal tissue dies and scar tissue forms. Both susceptibility and T2* maps were calculated to visualize iron in hemorrhages and validated by XRF Ca and Fe maps. The former was superior for imaging iron in hemorrhagic transformation and necrosis but did not capture ischemic lesions. In contrast, T2* could not differentiate Ca from Fe in necrotic tissue but did capture ischemic lesions, complementing the susceptibility mapping. The spatial localization, accurate quantitative data and elemental differentiation shown here could also be valuable for imaging other brain tissue damage with abnormal Ca and Fe content.

Synthesis of magnetic iron and iron oxide micrometre-sized composite particles of narrow size distribution by annealing iron salts entrapped within uniform porous poly(divinylbenzene) microspheres

This article describes a new simple approach to produce poly(divinylbenzene) and carbon micrometre-sized magnetic composite particles of narrow size distribution. For this purpose, uniform porous poly(divinylbenzene) microspheres were prepared by a single-step swelling of uniform polystyrene microspheres with divinylbenzene and benzoyl peroxide, followed by polymerization of the divinylbenzene within the swollen polystyrene particles. Uniform porous poly(divinylbenzene) microspheres were then formed by dissolution of the polystyrene part of the polystyrene–poly(divinylbenzene) composite particles. Iron salts, e.g., FeCl2·4H2O, dissolved in an organic continuous phase were then entrapped by vacuum within the pores of the cross-linked poly(divinylbenzene) microspheres. The obtained microspheres containing the iron salts were then annealed at 250 °C under ambient atmosphere. The formed magnetic microspheres were then annealed at 500 and 800 °C, respectively, under inert atmosphere. The annealing temperature allowed for control of the composition, crystallinity, size and size distribution and the magnetic properties of the obtained microspheres. Magnetic PDVB–α-Fe2O3 microspheres were obtained at 250 °C, while annealing of these microspheres at 500 and 800 °C under inert atmosphere leads to carbonization of the particles, and thereby the formation of C–Fe3O4 and air stable C–Fe microspheres, respectively. The magnetic moment of the C–Fe microspheres is notably high, 106.5 emu g−1. HR-TEM combined with STEM for elemental Fe mapping and imaging illustrated that by increasing the annealing temperature the size of the composite particles significantly decreased, while at the same time the size of the magnetic grains entrapped within the particles increased. Characterization of the various microspheres was also accomplished by other routine methods such as XRD, EDS, TGA, DSC, SQUID and Mossbauer spectroscopy.

Localization and Quantitative Analysis of Antigen−Antibody Binding on 2D Substrate Using Imaging NanoSIMS

Iron containing-antigen bound specifically to antibody immobilized on a surface is analyzed by nanoscale secondary ion mass spectrometry (NanoSIMS). This technique is well adapted compared with X-ray photoelectron spectroscopy and energy dispersive spectroscopy, which do not allow the detection of iron. The obtained Fe(+) map gives a good representation of the antigen repartition on the surface. NanoSIMS analysis of competition experiments performed with albumin and iron-free antigen are in good accordance with results obtained by a classical fluorescence microscopy approach. These results underline the interest of imaging NanoSIMS as a label-free method, allowing the localization and quantitative analysis of antigen-antibody binding with better spatial resolution than imaging ellipsometry and SPR.

A Coupled FE and DtN Mapping Method for the Exterior Problem of the Helmholtz Equation in an Oceanic Waveguide

The interaction of acoustic waves with a scattering object in an oceanic waveguide was considered. A finite-element method was developed to solve numerically the acoustic scattering problem based on the Galerkin variational principle and the DtN mapping method. The results show that the proposed method is valid and its numerical implementation is very fast. Moreover, the characteristics of the scattering waves by an obstacle in an oceanic waveguide and multiple scattering effects between the obstacle and the waveguide boundaries were numerically analysized.

Relation between photospheric magnetic field and chromospheric emission

Aims. We investigate the relationship between the photospheric magnetic field and the emission of the mid chromosphere of the Sun. Methods. We simultaneously observed the Stokes parameters of the photospheric iron line pair at 630.2 nm and the intensity profile of the chromospheric $\ion{Ca}{ii}$ H line at 396.8 nm in a quiet Sun region at a heliocentric angle of 53°. Various line parameters have been deduced from the $\ion{Ca}{ii}$ H line profile. The photospheric magnetic field vector has been reconstructed from an inversion of the measured Stokes profiles. After alignment of the Ca and Fe maps, a common mask has been created to define network and inter-network regions. We perform a statistical analysis of network and inter-network properties. The H -index is the integrated emission in a 0.1 nm band around the Ca core. We separate a non-magnetically, $H_{{\rm non}}$, and a magnetically, $H_{{\rm mag}}$, heated component from a non-heated component, $H_{{\rm co}}$ in the H -index. Results. The average network and inter-network H -indices are equal to 12 and 10 pm, respectively. The emission in the network is correlated with the magnetic flux density, approaching a value of $H \approx 10$ pm for vanishing flux. The inter-network magnetic field is dominated by weak field strengths with values down to 200 G and has a mean absolute flux density of about 11 Mx cm -2 . Conclusions. We find that a dominant fraction of the calcium emission caused by the heated atmosphere in the magnetic network has non-magnetic origin ($H_{{\rm mag}}\approx2\,$pm, $H_{{\rm non}}\approx3\,$pm). Considering the effect of straylight, the contribution from an atmosphere with no temperature rise to the H -index ($H_{{\rm co}}\approx6\,$pm) is about half of the observed H -index in the inter-network. The H -index in the inter-network is not correlated to any property of the photospheric magnetic field, suggesting that magnetic flux concentrations have a negligible role in the chromospheric heating in this region. The height range of the thermal coupling between the photosphere and low/mid chromosphere increases in presence of magnetic field. In addition, we demonstrate that a poor signal-to-noise level in the Stokes profiles leads to a significant over-estimation of the magnetic field strength.

Quantitative microanalysis of perineuronal nets in brain tissue

The relevance of the perineuronal nets (specialised extracellular matrix surrounding a part of the neurons in brain tissue) as a possible protection of neurons against oxidative stress induced by metal ions (e.g. Al, Fe, Cu and Zn) is an actually discussed hypothesis. It is assumed that the perineuronal nets are able to bind metal ions and thus reduce the oxidative stress to neurons. Therefore, we used nuclear microscopy (μPIXE) in order to investigate the concentration and distribution of iron in rat brain loaded with colloidal iron with special emphasis to the perineuronal nets in the extracellular matrix. The elemental microanalysis was performed on 6 μm thin resin embedded sections. The perineuronal nets accumulated more Fe than other extracelullar matrix components leading to well defined, neuron-related structures in the Fe maps. In order to quantify the affinity, the iron accumulations in the perineuronal nets were analysed for different Fe loadings. We present first results that support the hypothesis that perineuronal nets act as chemical protection mechanism against oxidative stress due to their ability to bind metal ions.

Analysis of interplanetary dust particles by soft and hard X-ray microscopy

Interplanetary dust particles (IDPs), fragments from asteroids and comets, contain important clues to the conditions in the solar nebula when dust was forming, provide evidence of the chemical and physical properties of their parent bodies, and may have been an important source of pre-biotic organic matter on the early Earth. We mapped the spatial distributions in IDPs of C, O, K, and Ca using a scanning transmission x-ray microscope and of Fe, Ni, Zn, Sr and Br using fluorescence microtomography. In addition, we obtained carbon and oxygen x-ray absorption near-edge structure (XANES) Spectra of the C-rich regions, identifying the C-ring and C=O functional groups, and Fourier Transform InfraRed (FTIR.) spectra, identifying the aliphatic C-H 2 and C-H 3 functional groups. The C-mapping indicates that IDPs contain anywhere from a few wt-% up to 90 wt-% carbon, much more carbon than is found in the most carbon-rich meteorites, and C- and O-XANES demonstrate that a significant fraction of this carbon is organic. The Ca, K, Fe, Ni, Zn, Sr, and Br maps allow inference of the host phases of these elements and place constraints on surface contamination.