Erratum to “Measurement of cross-sections for the (p, xn) reactions in natural molybdenum” [Nucl. Instr. and Meth. B 262 (2007) 171]

Using PIGE (TIARA, JAPAN) technique, we measured fluorine (F) uptake into the tooth enamel around a fluoride-containing material during caries progression using pH cycling. Class I cavities in the buccal surfaces of 6 extracted human teeth were drilled and filled with fluoride-containing material; a glass ionomer cement (Fuji IX(GC)). Three 300 μm sections through the material were obtained from each tooth. Two of these specimens were utilized to measure the F distribution in enamel adjacent to the material. A 1.7 MeV proton beam accelerated by the TIARA single-ended accelerator was delivered to a micro-beam apparatus. The beam spot size was about 1 μm with a beam current of about 100 pA. A nuclear reaction, ¹⁹F(p, αγ)¹⁶0, was used to measure the F concentration and the gamma-rays from this reaction were detected with a 4” NaI detector. X-rays induced by proton were detected with a Si(Li) detector to measure calcium concentration and the beam intensity was monitored with the X-ray yield from a copper foil for quantitative analysis. After measurement of F uptake, all specimens were polished to a thickness of 120 μm. In order to simulate daily acid challenges occurring in the oral cavity, the pH cycling (pH6.8–pH4.5) was carried out for 1, 3 and 5 weeks, separately. The duration that the solution remained below pH 5.5 was 37 min per cycle. The cycles were repeated 6 times per day with 2 h interval between cycles, and the specimens were kept in remineralizing solution for the rest of pH cycle. After pH cycling, F and calcium distribution of each specimen was evaluated using PIGE technique. The F distribution of the specimens before pH cycling clearly showed the F uptake from fluoride-containing material into enamel adjacent to the material. After pH cycling, the caries progression in all specimens was observed by the image of transverse microradiography (TMR). The depth of caries and mineral loss progressed with increasing the duration of pH cycling, although the enamel adjacent to the material remained a caries inhibition zone due to low rate of demineralization. With caries progression, fluorine accumulated in the subsurface of the caries lesion, while the outermost surface of the caries lesion gradually dissolved under increasing pH cycling. The data obtained using PIGE (TIARA, JAPAN) technique were useful to understand the fluorine benefit for preventing dental caries by means of fluoride-containing dental materials.     

“Point by Point” model calculation of prompt neutron emission data for Cm(SF) and Cm(SF)

This work is devoted to the modeling of the prompt neutron emission in the spontaneous fission of ^248,244Cm. The Point by Point model calculations of relevant quantities (like: the multi-parametric matrix ν(A, TKE), the fission fragment multiplicity as a function of fragment mass (usually named sawtooth) ν(A), fission fragment pair multiplicity as a function of total excitation energy ν_pair(TXE), total average prompt neutron multiplicity 〈ν_p〉 and spectra N(E), total average multiplicity as a function of the total kinetic energy 〈ν_p〉 (TKE) describe very well all existing experimental data.     

Radiation-induced ‘long-cell’ (macro-cell) corrosion in light water reactors

In previous papers, the author has established various ‘long-cell’ (akin to ‘macro-cell’) corrosion configurations that exist in nuclear power plants. Among these, the radiation-induced corrosion cell is an important mechanism since it plays a major role in the corrosion problems found in primary water of the nuclear power plants. There are numerous experimental evidences indicating a potential difference induced by radiation, however, the exact mechanism of such phenomena has not been clarified. The author investigated the basic mechanism by combining radiation chemistry, electrochemistry and corrosion science to confirm the existence of radiation-induced ‘long-cell’ action.By performing a competition kinetic study, , reacting mainly with stable molecules are found to be responsible for inducing a large portion of the potential difference both in the PWR and BWR water chemistry environments. The hydrated electrons react at a cathodic half-cell thereby inducing reductive reactions in the mixed cell configuration. This method reproduces the reported and experimentally observed redox potential variation to a certain extent (observed in the INCA Test Loop in Sweden and the NRI-Rez BWR-2 Loop in Czech Republic). The author believes the results support the assumed corrosion mechanism although details are still debatable.     

Erratum to “On the gas-solid difference in stopping power for low energy ions” [Nucl. Instr. and Meth. B 262 (2007) 13]

Recently, we claimed that the gas-solid difference in stopping powers persists from high down to low ion energies. This claim was based on a comparison between experimental data and the table of ICRU Report 73. We reconsider this claim in view of a recent article by Sigmund and Schinner where the claim was rejected. We find that the apparent gas-solid difference shown in our calculations is an artifact: it really points to an inadequacy of the table of ICRU 73 for low energy ions.     

功能化的β-环糊精水凝胶对U(Ⅵ)、Th(Ⅳ)的吸附

以顺丁烯二酸酐修饰的β-环糊精（β-CD）、丙烯腈(AN)和顺丁烯二酸酐(MAH)为单体，合成了功能化三元共聚物水凝胶β-CD/MAH-co-AN-co-MAH（CD-AN-MAH），进一步肟化得到β-CD/MAH-co-AO-co-MAH（CD-AO-MAH）。为了探索两种三元共聚物水凝胶在一定条件下对U(Ⅵ)、Th(Ⅳ)的吸附特性，研究了酸度、时间和温度对吸附过程的影响，进而观察U(Ⅵ)和Th(Ⅳ)的不同的吸附行为；结合动力学拟合、吸附等温线和热力学拟合解释U(Ⅵ)和Th(Ⅳ)与两种新材料间的相互作用机理。结果表明：一定酸度条件下，两种三元共聚物水凝胶对U(Ⅵ)和Th(Ⅳ)的吸附均是快速的动力学过程，服从准二级动力学模型；肟化后的CD-AO-MAH对U(Ⅵ)的吸附效果优于肟化前的CD-AN-MAH；且两种三元共聚物水凝胶对于U(Ⅵ)的吸附均优于对Th(Ⅳ)的吸附。再一次证明肟基对U(Ⅵ)有较好的选择性，肟化后的三元共聚物水凝胶可以做为选择性分离U(Ⅵ)的潜在材料。