Characterization of neutron field in the experimental fast reactor JOYO for fuel and structural material irradiation test

The experimental fast reactor JOYO has been operated as an irradiation test facility for fast reactor fuel and structural material since 1983 with its MK-II core. During this time, an extensive study was conducted to characterize the neutron field in order to assure the accuracy and reliability of neutron fluence. Neutron flux for a given irradiation test was calculated using a core management code system based on three-dimensional diffusion theory. It was then corrected with the adjusted neutron spectrum by means of the multiple foil activation method. The neutron fluence calculation accuracy in the fuel region was evaluated within a 5% error by comparing the burn-up of spent fuel with the measured values, which had been obtained from their post-irradiation examination. At positions away from the fuel region, the neutron flux distribution was calculated using a two-dimensional transport code. A Monte Carlo code was also used to analyze the detailed neutron flux distribution within an irradiation test subassembly that had a heterogeneous internal structure. With the neutron flux results various irradiation parameters, such as displacement per atom (dpa) and helium production, could be evaluated. A helium accumulation fluence monitor has been developed to measure not only neutron fluence but also helium production. Neutron flux and fluence obtained from the core management calculations were compiled as a database for users’ convenience together with related irradiation information and fuel subassembly material compositions. These data are expected to be widely used in the post-irradiation analysis of fuel and structural material.     

Improving the creep properties of 9Cr-3W-3Co-NbV steels and their weld joints by the addition of boron

New ferritic steels with a controlled addition of boron have been developed recently for ultrasuper-critical fossil power plants. These steels possess excellent creep resistance compared to conventional steels like P91, P92, P122, etc., and this has been attributed to the delay in coarsening of the carbides during creep owing to partial replacement of carbon by boron in these carbides. However, the susceptibility of the weld joints of the boron-containing ferritic steels to type IV cracking, which significantly brings down the rupture life of the weld joints, has not been investigated so far. In the present work, the creep properties of recently developed 9Cr-3W-3Co-NbV steels with boron contents varying from 47 to 180 ppm and of their weld joints have been studied. Creep tests were carried out at 923 K in the stress range of 140 to 80 MPa. Specimens were examined for particle coarsening using field-emission scanning electron microscopy, and the boron content in the precipitates was estimated using field-emission auger electron spectroscopy (FE-AES). The grain size of the parent metal and the heat-affected zone (HAZ) were estimated using electron backscattered pattern (EBSP) imaging. Results showed that the creep properties of the steels with 90 and 130 ppm boron and of their weld joints are superior to those of the P92 steels and its weld joints. Further, no weld joints exhibited type IV cracking. No significant coarsening of the carbides was observed, not only in the parent metal but also in the HAZ of the steels with ≥90 ppm of boron. In addition to the delay in carbide coarsening, the large prior-austenite grain size of the parent metal and the absence of a conventional fine-grained HAZ (FGHAZ) in the weld joints also seem to have a beneficial effect on improving the creep properties of these steels and their weld joints.     

Analgesic Mechanisms of Steroid Ointment against Oral Ulcerative Mucositis in a Rat Model

Despite the long history of use of steroid ointments for oral mucositis, the analgesic mechanism has not been fully elucidated. In this study, we examined the effects of triamcinolone acetonide (Tmc) on oral ulcerative mucositis-induced pain in conscious rats by our proprietary assay system. Based on evaluations of the physical properties and retention periods in the oral mucosa of human volunteers and rats, we selected TRAFUL^® ointment as a long-lasting base. In oral ulcerative mucositis model rats, TRAFUL^® with Tmc suppressed cyclooxygenase-dependent inflammatory responses with upregulations of glucocorticoid receptor-induced anti-inflammatory genes and inhibited spontaneous nociceptive behavior. When an ointment with a shorter residual period was used, the effects of Tmc were not elicited or were induced to a lesser extent. Importantly, TRAFUL^® with Tmc also improved oral ulcerative mucositis-induced mechanical allodynia, which has been reported to be independent of cyclooxygenase. Ca²⁺ imaging in dissociated trigeminal ganglion neurons showed that long-term preincubation with Tmc inhibited the hypertonic stimulation-induced Ca²⁺ response. These results suggest that the representative steroid Tmc suppresses oral ulcerative mucositis-induced pain by general anti-inflammatory actions and inhibits mechanical sensitivity in peripheral nerves. For drug delivery, long-lasting ointments such as TRAFUL^® are needed to sufficiently induce the therapeutic effects.     

Fabrication of high-power electric double-layer capacitors

The electrochemical behavior of activated carbon/carbon (AC/C) composite electrodes was investigated for high-power electric doublelayer capacitors (EDLCs). It was found that high-rate charge/discharge characteristics are affected by the resistance of the electrolyte phase in the pores of the electrode. The charge/discharge characteristics were improved by optimizing the pore-size distribution of the electrodes. The size and total volume of the macro-pores in the electrodes were controlled by mixing and burning out polymer spheres. A high-power EDLC (15V, 470 F), which can discharge as much as 500 A, was fabricated by using improved AC/C composite electrodes.     

Electrochemical study on Mn-substitution in LiFePO4 olivine compound

Olivine compounds LiFe_1−xMn_xPO₄ (0.0 < x < 0.4) were prepared by the solid-state reaction, and the electrochemical properties were studied in order to examine the effects of Mn²⁺-substitution. The substitution led to the modification of the electrochemical performance, such as initial capacity, capacity fading and polarization. From the cyclic voltammetry, it was found that the effective Li⁺ ionic diffusion coefficient was always larger in the charging process than in the discharging process and that it became larger with an appropriate amount substitution. The structural analysis on the chemical-delithiated compounds exhibited anomalous expansion of the unit cell along c-axis with the substitution, while the lattice parameters of the pristine compounds obeyed Vegard's law. The relationship between the Li⁺ ion diffusion and the bottle-neck area of (0 1 0) zigzag path was discussed. From the results, it was considered that Mn²⁺ had no direct contribution on the electrochemical reaction but influenced both electronic and ionic conductivities, which led to some modifications in the electrochemical performance.     

Dispersion Behavior of Barium Titanate Nanoparticles Prepared by Using Various Polycarboxylic Dispersants

The effects of the polycarboxylic dispersant structures on the crystallinity and sedimentation behavior of prepared BaTiO₃ nanoparticles were analyzed using four types of dispersants—ethylenediaminetetraacetic acid dipotassium salt (EDTA), trans -aconitic acid (TAA), ammonium acrylate–methyl acrylate co-polymer (PAA50), and sodium polyacrylate (PAA100). In the case of EDTA and TAA, the adsorbed ratio of the dispersants on BaTiO₃ nanoparticles was relatively low, and only slight improvement of sedimentation behavior was observed. On the other hand, in the case of PAA50 and PAA100, the adsorbed ratio was high, and the sedimentation behavior was gratefully improved. Next, in order to analyze the relationships among the additive amount of polycarboxylic dispersants, crystallinity, and sedimentation behavior, various amounts of PAA100 or PAA50 were treated in the synthesis solution. The sedimentation behavior of BaTiO₃ nanoparticles improved with increasing amounts of PAA100 and PAA50 while their crystal phase became amorphous. Adding PAA50 at a molar ratio of COO⁻/Ba²⁺=0.266 resulted in BaTiO₃ nanoparticles with the best dispersion stability in an aqueous media.     

Methyl 3‐Hydroxymyristate,a Diffusible Signal Mediating phc Quorum Sensing in Ralstonia solanacearum

Ralstonia solanacearum, a plant pathogenic bacterium causing “bacterial wilt” on crops, uses a quorum sensing (QS) system consisting of phc regulatory elements to control its virulence. Methyl 3‐hydroxypalmitate (3‐OH PAME) was previously identified as the QS signal in strain AW1. However, 3‐OH PAME has not been reportedly detected from any other strains, and this suggests that they produce another unknown QS signal. Here we identify (R)‐methyl 3‐hydroxymyristate [(R)‐3‐OH MAME] as a new QS signal that regulates the production of virulence factors and secondary metabolites. (R)‐3‐OH MAME was synthesized by the methyltransferase PhcB and sensed by the histidine kinase PhcS. The phylogenetic trees of these proteins from R. solanacearum strains were divided into two groups, according to their QS signal types—(R)‐3‐OH MAME or (R)‐3‐OH PAME. These results demonstrate that (R)‐3‐OH MAME is another crucial QS signal and highlight the unique evolution of QS systems in R. solanacearum.     

Total structures of colistin minor components

Structural characterization of the colistin (CL) components were carried out using Frit-fast atom bombardment liquid chromatography/mass spectrometry (Frit-FAB LC/MS), tandem mass spectrometry (MS/MS) and the amino acid analysis proposed by MARFEY, and the total structures of 4 minor components including the absolute configuration of the constituent amino acids were proposed. The structures of the minor components were the same as those of the main component colistin A or B except that L-leucine is replaced by L-valine or L-isoleucine.     

Spurious response sensitivity of two-way transceivers related to the 3rd-order nonlinearity of SAW filters

The spurious response sensitivities (SRSs) of two-way radio transceivers, as determined from the 3rd-order nonlinearities of SAW filters, are compared using two types of filter, the IIDT-type and a newly-developed SAW-resonator-coupled type, in high-power ( approximately 1 W) applications. The latter type is shown to result in an SRS which satisfies system specifications with sufficient margins.<>     

New low-loss broadband SAW filter using unidirectional IDTs with U-shaped MSCs

A new low-loss broadband SAW filter is presented. A new configuration using one pair of electrically connected IDTs with an optimum number of fingers, as well as unidirectional IDTs with U-shaped MSCs, is described. Experimental results with bandwidth as wide as 10% and loss as low as 3 dB are achieved. Very accurate computer-aided design of a low-loss filter with MSCs is obtained.