Influences of the ZrC coating process and heat treatment on ZrC-coated kernels used as fuel in Pu-burner high temperature gas-cooled reactor in Japan

ABSTRACT

The concept of Pu-burner high temperature gas-cooled reactor (HTGR) has been proposed to more safely reduce the amount of recovered Pu. In the Pu-burner HTGR concept, coated fuel particles with ZrC-coated yttria-stabilized zirconia containing PuO₂ (PuO₂-YSZ) kernels are employed for very high burn-up and high nuclear proliferation resistance. The role of ZrC layer is that of oxygen getter. CeO₂-YSZ kernels were fabricated to simulate the PuO₂-YSZ kernel and coated with a ZrC layer. In this study, we clarified that both Ce-rich grains and Zr-rich grains were densely distributed in surface regions of the as-fabricated CeO₂-YSZ kernel. However, we have already clarified that the surface region of the CeO₂-YSZ kernel coated with a ZrC layer was porous and mainly consisted of Zr-rich grains. These experimental results confirmed that Ce-rich grains were selectively corroded during the ZrC coating process. Then, the chemical stability of Zr-rich grains would be higher than that of Pu-rich grains. Thus, it would be more difficult to extract Pu from PuO₂-YSZ kernels (in which almost all grains are Zr-rich) than from PuO₂-YSZ kernels (in which many Pu-rich grains are included). Influences of the sintering of fuel compact on the microstructure of the ZrC-coated CeO₂-YSZ kernel is also reported.     

Structural strength prediction for porous titanium based on micro-stress concentration by micro-CT image-based multiscale simulation

For the design of porous titanium component, differently from its use as functional materials, structural strength prediction algorithm is proposed based on the micro-stress concentration analyzed by the multiscale simulation. The modeling of real microstructure is carried out by the image-based technique with X-ray micro-CT. The multiscale computational method consists of asymptotic homogenization and finite element mesh superposition (FEMS) techniques. A criterion is proposed to predict the nonlinearity initiation point in the load and displacement curve by means of micro-stress distribution expressed by histogram. Only the constituent's yield strength is referred regardless of the microscopic morphology. The originality of this paper lies in the validation of the homogenization process, the modeling guideline of micro-mesh superposition onto macro-mesh in FEMS, and the strength prediction algorithm. L-shaped components with different pore diameter were discussed in both experiment and simulation.     

Practical application of toxicogenomics for profiling toxicant-induced biological perturbations

A systems-level understanding of molecular perturbations is crucial for evaluating chemical-induced toxicity risks appropriately, and for this purpose comprehensive gene expression analysis or toxicogenomics investigation is highly advantageous. The recent accumulation of toxicity-associated gene sets (toxicogenomic biomarkers), enrichment in public or commercial large-scale microarray database and availability of open-source software resources facilitate our utilization of the toxicogenomic data. However, toxicologists, who are usually not experts in computational sciences, tend to be overwhelmed by the gigantic amount of data. In this paper we present practical applications of toxicogenomics by utilizing biomarker gene sets and a simple scoring method by which overall gene set-level expression changes can be evaluated efficiently. Results from the gene set-level analysis are not only an easy interpretation of toxicological significance compared with individual gene-level profiling, but also are thought to be suitable for cross-platform or cross-institutional toxicogenomics data analysis. Enrichment in toxicogenomics databases, refinements of biomarker gene sets and scoring algorithms and the development of user-friendly integrative software will lead to better evaluation of toxicant-elicited biological perturbations.     

Joint Delay-Power Multiple Packet Capture Scheme for Spread-Spectrum Slotted ALOHA Packet Radio Networks

In this paper, a joint delay-power multiple packet capture scheme, that can collect multiple packets simultaneously from different terminals with both delay and power captures, is presented. The corresponding joint delay-power capture probabilities for a spread-spectrum slotted ALOHA packet radio networks where all terminals use a common spreading code under Rayleigh fading with power control are derived. Throughput and delay performance of the spread-spectrum slotted ALOHA packet radio networks with the joint delay-power multiple packet capture effect are shown by our simulation results to be significantly improved compared with the existing schemes.     

Efficient biosynthesis of D-allose from D-psicose by cross-linked recombinant L-rhamnose isomerase: separation of product by ethanol crystallization

Mass production of a rare aldohexose D-allose from D-psicose was achieved in a batch reaction by crude recombinant L-rhamnose isomerase (L-RhI) cross-linked with glutaraldehyde. The D-psicose substrate was, in turn, mass produced from a naturally abundant ketohexose D-fructose by immobilized recombinant D-tagatose 3-epimerase (D-TE). At an equilibrium state, 25% of D-psicose was isomerized to D-allose, that is, 25 g of D-allose was obtained from 100 g of D-psicose. The D-allose product was easily separated and crystallized from the reaction mixture that contains 25%D-allose, 8%D-altrose and 67%D-psicose using ethanol. Empirically, approximately 338 g, that is, 90% of a theoretical overall yield for the purification of pure D-allose crystals was produced from 1.5 kg of D-psicose within 30 d using a constructed bioreactor. The cross-linked enzyme had an operative half-life of two months after repeated usages.     

Morphologic changes in boar sperm nuclei with reduced disulfide bonds in electrostimulated porcine oocytes

In pigs, failure of sperm nuclear decondensation has been reported after injection into oocytes. We examined the effects of pretreating sperm heads with Triton X-100 (TX-100) and dithiothreitol (DTT) and of electrical stimulation of oocytes after sperm head injection on time-dependent morphologic changes in sperm nuclei and in vitro development to the blastocyst stage. In experiment 1, spermatozoa were pretreated with 1% TX-100 and 5 mM DTT (T + D) or not treated, and then injected into in vitro matured oocytes. Electrical stimulation (1.5 kV/cm, 20 mus DC pulse) was applied to the oocytes 1 h after injection (stimulated group) or was not applied (unstimulated group). Some of the oocytes in each group were evaluated at hourly intervals until 10 h after injection for morphologic changes in the sperm nuclei. Unstimulated oocytes injected with untreated spermatozoa showed a delayed peak in the rate of nuclear decondensation (39.4-44.1%, 3-6 h after injection) compared with oocytes injected with T + D-treated spermatozoa (57.0% and 52.6%, 1 and 2 h, respectively). The rate of male pronucleus formation peaked 6 h after stimulation (by 40-60%) after injected oocytes had been stimulated with an electrical pulse, irrespective of whether or not the spermatozoa had been pretreated. In unstimulated oocytes, the rate of male pronucleus formation did not increase and stayed at the basal level (less than 20%) throughout the culture period, regardless of the sperm treatment. Thus, T + D treatment of spermatozoa did not affect completion of fertilization. In experiment 2, we evaluated the effects of electrical stimulation and sperm treatment with T + D on the rate of blastocyst formation and the mean number of cells per blastocyst. Oocytes stimulated after injection with either T + D-treated or untreated spermatozoa showed significantly higher percentages of blastocyst formation (24.8% and 27.1% respectively) than did unstimulated oocytes (1.1% and 4.1% for T + D-treated and untreated respectively; P < 0.01 by Duncan's multiple-range test). The rate of blastocyst formation did not differ between the T + D-treated and untreated groups. The mean number of cells per blastocyst did not differ among any of the groups (14.0-29.4 cells). These results suggest that pretreatment of sperm with TX-100 and DTT shifted the timing of sperm nuclear decondensation forward. However, pronucleus formation and development to the blastocyst stage in vitro were not improved by sperm treatment. Thus, electrical stimulation of injected oocytes enhances in vitro development to the blastocyst stage in pigs.     

Performance of a room-temperature rotary magnetic refrigerator

We have designed and operated a rotating-magnet type AMR (active magnetic regeneration) refrigerator that uses water as a heat transfer fluid. Four kinds of gadolinium-based alloy are used as magnetic materials. A magnetic field of 0.77 T is applied by neodymium permanent magnets. The refrigerator produces a maximum cooling power of 60 W around 10 °C. An optimal time for one cycle exists, and it depends on the water flow rate and the frequency of magnetization and demagnetization. Enhancement of the water flow rate and the frequency is known to be essential for increasing the cooling power of this refrigerator.     

Multiple label-free detection of antigen-antibody reaction using localized surface plasmon resonance-based core-shell structured nanoparticle layer nanochip

In this research, a localized surface plasmon resonance (LSPR)-based bioanalysis method for developing multiarray optical nanochip suitable for screening bimolecular interactions is described. LSPR-based label-free monitoring enables to solve the problems of conventional methods that require large sample volumes and time-consuming labeling procedures. We developed a multiarray LSPR-based nanochip for the label-free detection of proteins. The multiarray format was constructed by a core-shell-structured nanoparticle layer, which provided 300 nanospots on the sensing surface. Antibodies were immobilized onto the nanospots using their interaction with Protein A. The concentrations of antigens were determined from the peak absorption intensity of the LSPR spectra. We demonstrated the capability of the array measurement using immunoglobulins (IgA, IgD, IgG, IgM), C-reactive protein, and fibrinogen. The detection limit of our label-free method was 100 pg/mL. Our nanochip is readily transferable to monitor the interactions of other biomolecules, such as whole cells or receptors, with a massively parallel detection capability in a highly miniaturized package. We anticipate that the direct label-free optical immunoassay of proteins reported here will revolutionize clinical diagnosis and accelerate the development of hand-held and user-friendly point-of-care devices.     

Electrochemical genosensor based on peptide nucleic acid-mediated PCR and asymmetric PCR techniques: Electrostatic interactions with a metal cation

The unique structure of peptide nucleic acids (PNAs), linking the N-(2-aminoethyl)glycine units that create a neutral backbone, and prevent it from acting as a primer for DNA polymerase, has been utilized in an electrochemical biosensor scheme for simple and sensitive detection of hybridization. When the PNA is targeted against a single-nucleotide polymorphism (SNP) or wild-type site on the gene, PNA-mediated polymerase chain reaction (PCR) clamping method effectively blocks the formation of a PCR product. In our report, PNA probe for PCR clamping was targeted against the wild-type site of alcohol dehydrogenase. The electrostatic interactions between the negatively charged DNA and neutral PNA molecules with redox-active metal cation cobalt(III)hexamine ([Co(NH3)6]3+) were monitored using differential pulse voltammetry. The electrostatic binding of [Co(NH3)6]3+ to DNA provided the basis for the discrimination against PNA/PNA, PNA/DNA, and DNA/DNA hybrid molecules. We have optimized the experimental conditions, such as probe concentration, [Co(NH3)6]3+ concentration, accumulation time for [Co(NH3)6]3+, and target concentration. A new pretreatment method has also been employed to allow fast and simple detection of hybridization reaction between the PCR amplicon and the probe on glassy carbon electrode (GCE) surface. This method was based on the application of a high-temperature treatment (95 degrees C, 5 min), followed by a 1-min incubation in the presence of DNA primers. The excess concentration of DNA primers prevented the rehybridization of the denatured strands, while enabling the target gene sequence to bind with the immobilized probe. Additionally, asymmetric PCR was employed to detect the presence of genetically modified organism in standard Roundup Ready soybean samples. The amplicons of asymmetric PCR, which were predominantly single-stranded DNA as a result of unequal primer concentration, hybridized with the DNA probe on the sensor surface efficiently. The attachment of long single-strands on GCE surface caused the accumulation of [Co(NH3)6]3+ and a high current response. Here, we report a versatile method that would allow for simple and rapid analysis of nucleic acids in combination with PNA-mediated PCR and asymmetric PCR techniques by using an electrochemical genosensor.