Distribution Of Elements In Samples Research Articles

Stratigraphic characterization of ancient Roman frescos by laser induced breakdown spectroscopy and importance of a proper choice of the normalizing lines

In order to answer to some specific unsolved questions regarding ancient Roman frescoes from Villa della Piscina, already examined by other spectroscopic techniques, LIBS stratigraphic measurements were performed on the most representative sample fragments. We found that taking into account just the line intensities or applying a single normalization approach based on ratio of the element's analytical line and a selected transition from a main sample constituent, here of Ca, might produce misleading results of depth profiling by LIBS. During the laser induced ablation, parameters of the detected plasma might change both due to the crater development and different overlaid matrix materials, as in case of heterogeneous painted samples, possibly realized with different techniques. We performed the theoretical simulations to select the pair of Cu I and Ca I lines less sensitive to variations of the plasma temperature in presence of local thermal equilibrium (LTE). However, when using not gated detectors as here, the experimental results showed that only a partial LTE holds. For this reason, the choice of the optimum normalization line must take into account also the energy gap between the excited levels of the species, which energies affect the emission lifetime and consequently, the intensity captured by not gated detectors. In following, to the each element's analytical line a specific Ca I line was attributed for deducing the relative element distribution in sample. Following this approach and by detecting simultaneously up to 20 elements per laser pulse, it was possible to distinguish clearly by LIBS also thin overpainted layers of similar colour, and to recognize the painting technique used. Through detection of trace and light elements and studies of their correlations with other elements during ablation of on painted layer, in some cases it was possible also to establish the geographical provenance of the material used.

A compact imaging system with a CdTe double-sided strip detector for non-destructive analysis using negative muonic X-rays

A CdTe double-sided strip detector (CdTe-DSD) is an ideal device for imaging and spectroscopic measurements in the hard X-ray range above 10 keV. Recent development enables us to realize an imager with a detection area of ∼10 cm2. An energy resolution of 1–2 keV (FWHM) and a position resolution of a few hundred μm are available from the detector. This type of imager has been long awaited for non-destructive elemental analysis, especially by using negative muons, because energies of characteristic X-rays from muonic atoms are about 200 time higher than those from normal atoms. With the method that uses negative muons, hard X-ray information gives the spatial distribution of elements in samples at a certain depth defined by the initial momentum of the muon beam. In order to study three-dimensional imaging capability of the method, we have developed a compact imaging system based on CdTe-DSD and a ϕ 3 mm pinhole collimator as the first prototype. We conducted experiments with samples which consist of layers of Al, BN and LiF irradiated by negative muon beams in MUSE/J-PARC and successfully reconstruct hard X-ray images of muonic X-rays from B, N and F at various depths.

First results of the application of scanning XRF analysis with synchrotron-radiation beams from the VEPP-3 to study the spatial distribution of trace elements in samples of stratiform chromite ores

A sample from chromite horizon UG1 of the platiniferous Bushveld complex (South Africa) is studied by scanning X-ray fluorescence (XRF) microanalysis using synchrotron-radiation beams from the VEPP-3 storage ring. The sample contains plagioclase and chromite layers 3–5 mm in thickness. The experimental study is conducted at excitation energies of 15 and 30 keV; the spot size of the excitation radiation is 0.1 ± 2 mm; and the scanning step is 100 µm. The distribution profiles of more than 20 trace elements over the surface of the sample are obtained.

Self-assembly preparation of SiO2@Ni-Al layered double hydroxide composites and their enhanced electrorheological characteristics.

The core-shell structured SiO2@Ni-Al layered double hydroxide (LDH) composites were prepared via self-assembly of Ni-Al LDH on the surface of SiO2 spheres. Only coating a layer of ultrathin Ni-Al LDH sheet, the resulting SiO2@Ni-Al LDH composites exhibit significantly enhanced electrorheological (ER) characteristics compared to conventional bare SiO2 spheres. The monodispersed SiO2 spheres with average diameters of 260 nm were synthesized by the hydrolysis of tetraethyl orthosilicate (TEOS), while the shell part, Ni-Al LDH sheet was prepared by the hydrothermal procedure. The morphology of the samples was investigated via scanning transmission electron microscopy (STEM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The structure of the samples was characterized by X-ray diffraction (XRD). The species and distribution of elements in samples were confirmed by X-ray photoelectron spectroscopy (XPS), Energy dispersive analysis of X-ray (EDX) and elemental mapping in STEM. Subsequently, the ER characteristics of the composites dispersed in insulating oil were characterized by a rotational rheometer. The electric field-stimulated rheological performances (yield stress, viscosity, modulus, etc.) were observed under an external electric field, which is different from the Newtonian state in the free electric field.

Imaging of trace elements in tissues: with a focus on laser ablation inductively coupled plasma mass spectrometry.

Elemental imaging techniques are capable of showing the spatial distribution of elements in a sample. Their application in biomedical sciences is promising, but they are not yet widely employed. The review gives a short overview about techniques available and then focuses on the advantages of using laser ablation inductively coupled plasma mass spectrometry for elemental bioimaging. Current examples for the use of elemental imaging with medical context are given to illustrate the potential of this type of analysis for clinical applications. Recently, synchrotron-based techniques and laser ablation inductively coupled plasma mass spectrometry have been successfully applied to analyse the spatial distribution of elements in biological samples of medical relevance. Elemental bioimaging methods have a great potential for medical applications. They are complementary to molecular imaging and histological staining and are especially attractive when used in combination with stable isotope tracer experiments.

Transition Edge Sensor-Energy Dispersive Spectrometer (TES-EDS) and Its Applications

The Transition Edge Sensor (TES)-Energy Dispersive Spectrometer (EDS) is an X-ray detector with high-energy resolution (12.8eV). The TES can be mounted to a scanning electron microscope (SEM). The TES-EDS is based on a cryogen-free dilution refrigerator. The high-energy resolution enables analysis of the distribution of various elements in samples under low acceleration voltage (typically under 5keV) by using K-lines of light elements and M lines of heavy elements. For example, the energy of the arsenic L line differs from the magnesium K line by 28eV. When used to analyze the spore of the Pteris vittata L plant, the TES-EDS clearly reveals a different distribution of As and Mg in the micro region of the plant. The TES-EDS with SEM yields detailed information about the distribution of multi-elements in a sample.