K. Masumoto

Systematic study of foreign-atom-doped fullerenes by using a nuclear recoil method and their MD simulation

The formation of atom-doped fullerenes has been investigated by using several types of radionuclides produced by nuclear reactions. It was found that the endohedral fullerenes (Kr@C60,u2009u2009Xe@C60) and their dimers, furthermore, heterofullerenes, such as AsC59, GeC59 and their dimers, are produced by a recoil process following nuclear reactions. Other nuclear reaction products (Na, Ca, Sc, etc.) may destroy most of the fullerene cage in the same process. Carrying out ab initio molecular-dynamics simulations based on an all-electron mixed-basis approach, we confirmed that the formation of Kr- (or Xe-) atom-doped endohedral fullerenes and of substitutional heterofullerenes doped with an As atom is really possible. The experimental and theoretical results indicate that the chemical nature of doping atoms is important in the formation of foreign-atom-doped fullerenes.

A new internal standard method for activation analysis and its application. Determination of Co, Ni, Rb, Sr in pepperbush by means of photon activation

A new internal standard method for activation analysis has been developed. This method is characterized by that a suitable element present originally in the sample is used as an internal standard and the comparative standard is prepared by applying the standard addition method to the duplicated sample. When a sample under examination contains Wag of trace element A to be determined together with a known amount of element B which is usable as an internal standard, and when the comparative standard is prepared by adding Wa* g of accurately known small amount of the element A to the duplicated sample, even if the sample and comparative standard are irradiated separately by particles with different fluxes, Wa can be determined, easily by using the following equation: Wa=Wa*/[(AR*/AR)-1] Where AR and AR* are counting ratios of gamma-rays emitted by two radioactive nuclides produced from the element A and B in the sample and comparative standard, respectively. Neither correction of the inhomogeneities of flux between the sample and comparative standard, nor that of, the self-shielding effects are necessary for the present method. The usefulness of the method was examined through the determination of Co, Ni, Rb and Sr in pepperbush by means of photon activation, and the precision and accuracy of the method were proved to be valid.

The yields of photonuclear reactions for multielement photon-activation analysis

A comprehensive study on the yields of photonuclear reactions of various types has been performed, and sensitivities and the effects of interferences in multielement photon-activation analysis have been evaluated by bremsstrahlung activation of many elements with maximum energies ranging from 30 to 60 MeV. The applicability and reliability of the method were demonstrated by analyzing standard round-robin samples and then by presenting the elemental abundances in several geological, biological and environmental materials. The method was almost insensitive to matrix effects and was assessed to be promising for nondestructive multielement determination of the materials of wide variety, giving good reproducible results for 20 or more elements.

Activation yield curves of photonuclear reactions for multielement photon activation analysis

Abstract The activation yield curves have been presented for a number of photonuclear reactions in the energy range from 30 to 68 MeV, in order to evaluate quantitatively the interferences due to competing reactions in multielement photon activation analysis. The general features of the yields as functions of both target mass number and excitation energy were elucidated from the data obtained, discussion being given on the results in terms of the reaction mechanism. Simultaneous neutron activation due to appreciable neutron production from the converter and surrounding materials has also been studied, and, finally, the magnitudes of interferences in real multielement analysis were given in the form of their energy dependences.

Simultaneous determination of P, Cl, K and Ca in several control serums by alpha-particle activation analysis using the internal standard method

In order to demonstrate the usefulness of alpha-particle activation analysis, simultaneous determination of P, Cl, K and Ca in commercially available control serums has been studied fundamentally. After thick target yield curves of radionuclides produced from the element to be determined were measured as a function of alpha energy together with those of the interferences, an optimum working standard for the present experiments was provided by applying the internal standard method to a human serum under the most suitable bombardment conditions. Then, the concentrations of the above four elements in several control serums were determined efficiently and reasonably by ordinary alpha-particle activation analysis.

Formation of dimer, trimer, and tetramer of C60 and C70 by γ-ray, charged-particle irradiation, and their HPLC separation

Abstract C60 and C70 fullerenes were irradiated by high-energy γ-rays and charged particles. Coalesced products of C60 and C70 have been isolated and detected in the liquid phase by a radiochromatographic technique. It was found that not only 11 C radioactive fullerene dimer, trimer, and possibly tetramer were produced by a recoil implantation process following nuclear reaction, but also such non-radioactive coalesced products were produced by the recombination process after ionization by γ-rays or charged particles.

Stable-isotope dilution activation analysis, and determination of Ca, Zn and Ce by means of photon activation

AbstractAs a new method, stable-isotope dilution activation analysis has been developed. When an element consists of at least two stable isotopes which are converted easily to the radioactive nuclides through nuclear reactions, the total amount of the element (xg) can be determined by irradiating simultaneously the duplicated sample containing small amounts of either enriched isotope (y g), and by using the following equation.n% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaaSGbaeaaie% aacaWF4bGaa8xpaiaa-LhadaqadaqaamaalyaabaGaa8xtaaqaaiaa% -1eacaWFQaaaaaGaayjkaiaawMcaamaadmaabaWaaeWaaeaadaWcga% qaaiaa-jfacaWFQaaabaGaa8NuaaaaaiaawIcacaGLPaaadaqadaqa% amaalyaabaGaeqiUde3aa0baaSqaaiaaikdaaeaacaGGQaaaaaGcba% GaeqiUde3aaSbaaSqaaiaaikdaaeqaaaaaaOGaayjkaiaawMcaaiab% gkHiTmaabmaabaWaaSGbaeaacqaH4oqCdaqhaaWcbaGaaGymaaqaai% aacQcaaaaakeaacqaH4oqCdaWgaaWcbaGaaGymaaqabaaaaaGccaGL% OaGaayzkaaaacaGLBbGaayzxaaaabaWaamWaaeaacaaIXaGaeyOeI0% YaaeWaaeaadaWcgaqaaiaa-jfacaWFQaaabaGaa8NuaaaaaiaawIca% caGLPaaaaiaawUfacaGLDbaaaaaaaa!5A36!nn

INSTRUMENTAL CHARGED-PARTICLE ACTIVATION ANALYSIS OF SEVERAL SELECTED ELEMENTS IN BIOLOGICAL MATERIALS USING THE INTERNAL STANDARD METHOD

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