International Journal of PIXE

During the examination of the representative specimens, a barite ore and a polymetallic chimney, from the JADE hydrothermal field of Okinawa Trough, many amorphous silica globules of approximately 10 to 50 micrometers in diameter were found as isolated sphere or bunchy aggregation. We performed micro-PIXE analyses of the globules to check the effectiveness of the method to such soft and vulnerable material, and to understand the geochemical characteristics. The result shows that amorphous silica can include various kinds of elements in lithophile, chalcophile and siderophile categories. The trace element distribution of the globules indicates that amorphous silica could be a good monitor of geochemical environment; and implies that the chemical variation of ore often found in a mineral field is mainly derived by change in local physicochemical conditions of single mineralizing fluid rather than multiple injection of the solution.

Trace elements are known to have pivotal role in human health and disease. Present investigation employed PIXE analysis to probe into the elemental profile of patients suffering from visceral Leishmaniasis. Remarkable alterations were observed in concentration of elements like Cl, K, Ca, Mn, Fe, Cu, Zn. The pattern of enhancement of elemental concentration corresponds to the progression of the disease. Additionally, our present data reflect probable correlation between alteration in trace elemental status and other pathological syndromes associated with Leishmaniasis. The possibility of considering trace elements as a diagnostic marker for a better understanding of the disease is discussed.

Priming X-irradiation with 0.3-0.5 Gy induces radio-resistance in C57BL/6 strain of mice 2 weeks afterward. Elements in the bone marrow, sampled 11 days after challenging exposure to 5.0 Gy, were determined by PIXE. The challenging irradiation decreased Mg, P, S, K, Ca and Zn as well as dried bone marrow weight. The pre-irradiation enhanced recovery of these levels, indicating stimulated recovery of the metabolism in the tissue. Fe in both control (without pre-irradiation) and experimental groups increased to about twice the original value, showing elevated hemoglobin synthesis after challenging exposure. In previous studies we have reported that recovery of peripheral blood cell counts after sub-lethal irradiation was enhanced by the pre-irradiation. Further, study on accumulation of p53 and Bax proteins, which lead to apoptotic cell death, revealed that the pre-irradiation significantly suppressed accumulation of these proteins in the spleen after challenging irradiation with 3 Gy. These results and our present study suggest that the pre-irradiation decreased the spleen cell death, and favored re-growth of the spleen cells, resulting in stimulated recovery of metabolism for hematopoiesis in the bone marrow as well as in the spleen after challenging high dose irradiation. Stimulated recovery of Mg, P, S, K, Ca and Zn levels might indicate the importance of these elements in hematopoiesis.

Marine micro-algae (Nannochloropsis sp., and Phaeodactylum sp.,) were obtained from the Pacific Ocean of Iwate Pref., Japan and purely cultured in nutritive seawater as a culture solution. The culture size for algae was 10 - 250 ml and every apparatus was small and of low cost. Marine micro-algae were given in different culture solutions including Pb²⁺ from 0.01 to 1.0 mg /l. The algae in 5 ml of the culture solution were collected on a polycarbonate filter (pore size : 1.0 μm) by suction filtration. The algae on the filter were subjected to PIXE analysis. Concentrations of Na, Mg, Si, P, S, Cl, K, Ca, Cr, Mn, Fe, Cu, Zn, Sr and Pb were simultaneously determined. PIXE can do multi-element analysis for a sample of below 1 mg. The quantity of lead in marine micro-algae increases in proportion to the Pb²⁺ concentration in the culture solution. The concentration factor (wet weight base) for lead is given as 200 ± 20 ml / g for Nannochloropsis sp. and 1900 ± 400 ml / g for Phaeodactylum sp.. It is shown that PIXE is a powerful tool for the measurement of the bioaccumulation of trace elements.

Bio-medical implants release metallic elements during the long periods of time while inserted in the human body. The chemical interactions between the tissues and surface of the implants, and the mechanical friction of implants cause the release of metals into the human tissues. In this study we investigated the distribution and the chemical-state of the metallic elements in the tissues around a failed implant system using PIXE (proton induced x-ray emission) and SR-XRF (synchrotron radiation x-ray fluorescence) spectroscopies. The specimens were from the cases of patients with diagnosed arthritis. The implant consisted of a stem and a metal backing made of Ti-6Al-4V, an implant head made of stainless steel, and a polyethylene (PE) cup. Both the stem and the metal backing had a plasma-sprayed HAp surface coating. Distribution and concentration of dissolved elements in tissues surrounding implants were examined and quantified using PIXE analysis. Similar specimen from the same case was further investigated using SR-XRF analysis. Chemical-states of the dissolved elements ware also studied by XAFS (x-ray absorption fine structure) analysis. From results of these measurements, it is confirmed that the tissues surrounding implants contained metallic elements such as Fe, Cr, Ni, and Ti. These elements are originated from the implant. Furthermore, it was made clear that the chemical-state of Fe had changed as a consequence of dissolution of Fe in the organic tissues.

Chemical shifts of Kα_1,2 line of sulfur in marine sediments were measured with in-air high-resolution PIXE in order to examine the possibility of direct speciation of sulfur in such environmental substances. Change of chemical states of sulfur along the depth in the sediments was observed. Oxidation of the sediment samples by air was also examined. Problems to be improved for exact speciation are discussed.

Transition metal elements and others in river water sample supplied by The Japan Society for Analytical Chemistry (JSAC) were determined by PIXE using 2.5 MeV proton beam at the Tokyo Institute of Technology Van de Graaff Laboratory. The relative detection efficiency for each X-ray of element and its recovery were studied in two methods: "Drop and Dry" and "Concentration" methods. Ten elements (V, Cr, Mn, Fe, Ni, Cu, Zn, As, Se and Pb) were determined, being in good agreement with the values certified by JSAC except for Mn. Intensity of K_α X-ray of As and L_α, X-ray of Pb nearly close to each other could be successfully evaluated using isolated L_β X-ray of Pb. Mn was insufficiently recovered to give lower content than the certified value in the present conditions. V that is not listed in the certificate was found to show good agreement with that reported previously. Concentration method using sodium dibenzyldithiocarbamate only could be successfully employed for collecting these elements.

The alignment effect on the L-shell ionization of Nb atom (Z=41) by 0.84MeV, 1.38MeV and 2.92MeV proton impact was investigated. The polarization of L_ℓ X-rays emitted from the aligned niobium target was measured with the crystal spectrometer combined with a position sensitive proportional counter. The experimental values of the degree of alignment A₂ were compared with the prediction of PWBA theory. It results that the experimental value of A₂ in 1.38MeV proton impact was much larger than the theoretical one, and A₂ of 0.84MeV almost coincides with that of 2.92MeV.

Micro-beam scanning system for PIXE analysis newly installed in National Institute of Radiological Sciences (NIRS) was introduced in this paper. Fine ring structure of a fish scale was observed using elemental mapping with proton micro-beam scanning. Pollen was analyzed as one example of single cell to demonstrate the elemental distribution. The minimum size of the proton beam is estimated as 0.4×0.65 μ m.