International Journal of PIXE

This study aimed to investigate the effect of the particles releasing chitosan upon exposure to radiation on inhibition of metastasis.

A 10 mL solution of water containing 0.2% weight/volume alginate, 0.1% hyaluronic acid, and 100-mg chitosan was sprayed into the vibrating solution through a stainless mesh filter (pore size: 0.8 $\mu$m) using an ultrasound disintegrator, thereby generating chitosan particles. Further, $1\times 10^{10}$ particles floating in 0.1 mL normal saline were subcutaneously injected around the 4TI cells-derived tumor in the left hind legs of six-week-old male C3He/N mice. Six hours after injection, tumors were exposed to 10 Gy or 20 Gy of 100-keV soft X-ray radiation. The release of chitosan was expressed as the frequency of ruptured chitosan particles 12 h after radiation. The antimetastatic effect was confirmed by a reduction in the number of metastatic pulmonary nodules 21 days after completion of treatment.

More than $56.3\pm 4.3$% of the chitosan particles released chitosan in response to radiation. The particles releasing chitosan had a prolonged antimetastatic effect when compared with the particles not releasing chitosan, thereby resulting in a significantly greater antimetastatic effect lasting for four weeks since the completion of treatment, in tumors treated with both 10 Gy and 20 Gy of radiation.

Hence, particlizing chitosan could be useful in reducing metastasis in irradiated tumors.

Tooth-bound (KOH-insoluble) fluoride prevents caries via long retention within the tooth structure. Tooth-bound fluoride in the enamel was investigated after applying various fluoride-containing tooth-coating materials using an in-air micro $(\mu )$ PIXE/PIGE system. Three different fluoride-containing or a non-fluoride containing coating materials were applied to the coronal enamel surface of 24 extracted human molars. The samples were stored in water for 1 or 7 days and then sectioned into two slices. One slice was immersed in 1M KOH solution for 24 h for KOH-insoluble fluoride (KOH(T)) analysis. The second slice was not subjected to KOH treatment and was used to analyze the whole fluoride (KOH-soluble plus insoluble fluoride: KOH(U)). Fluorine and calcium distribution were measured in all the slices with $\mu$PIXE/PIGE. KOH(U) was higher than KOH(T) on some materials, especially those that released more fluoride. For KOH(T), there was no significant difference among all fluoride-containing materials in the 7-day group. However, there were significant differences in the KOH(U) samples during the same period. PIXE/PIGE analysis confirmed the presence of tooth-bound fluoride in the enamel adjacent to the fluoride-containing coating materials. The amount of tooth-bound fluoride depended on the type of material.

The spent PUREX solvent containing U and Pu is generated from the reprocessing process of spent nuclear fuel. The nuclear material removal is important for the safe storage or disposal of the spent solvent. Our previous study revealed that the adsorbent with the iminodiacetic acid (IDA) functional group is one of the most promising materials for designing the nuclear material recovery process. Accordingly, an IDA-type adsorbent was synthesized by using graft polymerization technology or a chemical reaction to improve the adsorption rate and capacity. The synthesized IDA-type adsorbent was characterized by micro particle-induced X-ray emission (PIXE) and extended X-ray absorption fine structure (EXAFS) analyses. The micro-PIXE analysis revealed that Zr was adsorbed on the whole synthesized adsorbents and quantified the microamount of adsorbed Zr. Moreover, EXAFS suggested that Zr in the aqueous solution and solvent can be trapped by the IDA group with different mechanisms.

Analysis of cultural heritage samples by PIXE involves the risk of damaging precious samples due to MeV-proton irradiation. To investigate appropriate methods to detect invisible damage due to PIXE analysis, we analyzed the change in chemical bonding of the sample surface subjected to PIXE and RBS measurement by Fourier Transform InfraRed spectroscopy (FT-IR). We used Japanese hemp paper as a simulated cultural property sample. The proton irradiation for the PIXE/RBS measurement was performed in a vacuum with an incident beam energy of 2.5 MeV, a beam current of 1 nA, and an irradiation time up to 10 min. The corresponding beam flux and fluence were 0.06 nA/mm² and 4 $\mu$Coulomb/cm², respectively. When the irradiation time was 10 min, the absorbed dose was 480 kGy on the sample surface. We identified neither change of elemental composition nor visible change such as discoloration due to irradiation. However, we found changes in peak heights in the measured FT-IR spectra, which suggest the destruction of chemical bonds such as O–H and C–O due to proton-induced radiation damage.

More than 4000 beard samples were collected from a single person every morning over a 12-year period and analyzed using a standard-free method. We detected significant annual variations in the concentrations of magnesium and calcium in the study period, although significant monthly and seasonal variations were not noted. Calcium tends not to be obtained from season-specific foods or drinks, so its variations may be affected by changes in the metabolism of the body. In contrast, however, potassium showed marked long-term variations with significant seasonal differences. As our previous studies confirmed that green vegetables contain large quantities of potassium and that their supply and consumption increase from May to July, the seasonal variations in potassium concentration were attributed to the ingestion of green vegetables. Although magnesium is also contained in green vegetables in large quantities, its principle supply sources are diverse and its concentration did not show any clear seasonal changes.

For the first time, particle-induced X-ray emission (PIXE) spectra were obtained using TlBr detectors. The TlBr detector was fabricated from a crystal grown with material purified by the zone purification. Its active volume was 1.5 mm × 1.5 mm × 3.1 mm, and it exhibited an energy resolution of a 6.2 keV full-width at half-maximum (FWHM) for 59.5 keV at room temperature. The detector was installed into a PIXE system at Aomori Prefecture Quantum Science Center. A Pb plate target in the PIXE chamber was irradiated with a 20 MeV proton beam, and X-ray peaks for Pb K${}_{\alpha }$ and K${}_{\beta }$ were successfully detected by the TlBr detector at room temperature.

To characterize the chemical composition of aircraft exhaust particles, we developed a treatment method of jet fuel for an elemental analysis by an in-vacuum PIXE system. Eleven elements (Si, S, Cl, K, Ca, Cr, Fe, Ni, Cu, Zn, and Pb) were identified from each sample. The concentrations of S from five JET A-1 fuel samples collected on different days ranged from 30.4 to 440 wt.-ppm. The concentration level of S agreed well with the measurement results obtained by an in-air PIXE analysis, which we have previously performed to determine the major content elements and their concentration levels. Nine elements out of the identified 11 elements (Si, Cl, K, Ca, Cr, Ni, Cu, Zn, and Pb), which were not detected by the in-air PIXE analysis, were detected in all the JET A-1 fuel samples measured. Among these elements, Si, Ni, Cu, Zn, and Pb were found to be the major components. It is suggested that particles emitted from aircraft jet engines, which are generally in the size range smaller than 100 nm (ultrafine particles: UFPs), may contain Si, Ni, Cu, Zn, and Pb. These findings provide useful insights into the source apportionment of UFPs in and around airports.

The Zr and Mo removal from HLLW is the current issue for repeated usage of the CMPO/SiO₂-P-packed column. The adsorbability of the 2-mm-sized HDEHP/SiO₂-P adsorbent, which was prepared by fabricating a SiO₂ particle from the vibration cutting method and adapting a new polymerization method, was evaluated by the batch-wise adsorption experiment. In spite of the impregnation ratio of the HDEHP extractant, the extraction of Zr and Mo ions from the simulated HLLW was achieved but lanthanide ions e.g., Nd and Gd were also extracted as a minor component. Such unusual adsorption behavior of lanthanide ions could be only provided by accurate, sensitive and reliable micro-PIXE analysis.

In this paper, we performed PIXE analysis of trace elements in freshwater pearls cultured in four different areas: Lake Biwa (Japan), Lake Kasumigaura (Japan), an unidentified lake in China, and Kentucky Lake (USA). We investigated the difference of trace elements contained in the four pearls from different aquaculture environments. The observed trace elements are Mn, Fe, Cu, Zn, and Sr. The major trace elements are Mn, Sr for all the samples. From comparison of the proportions of elements contained, we found the following features: (1) The Kasumigaura pearl has a nucleus with a high Mn/Sr ratio, (2) The Biwako pearl is low in iron content, and (3) The American pearl has high in Fe/Sr, Cu/Sr, and Zn/Sr ratios.