Fracture criteria of reactor graphite under multiaxial stesses

New fracture criteria for graphite under multiaxial stresses are presented for designing core and support materials of a high temperature gas cooled reactor. Different kinds of fracture strength tests are carried out for a near isotropic graphite IG-11. Results show that, under the stress state in which tensile stresses are predominant, the maximum principal stress theory is seen as applicable for brittle fracture. Under the stress state in which compressive stresses are predominant, there may be two fracture modes for brittle fracture, namely, slipping fracture and mode II fracture. For the former fracture mode the maximum shear stress criterion is suitable, but for the latter fracture mode the following mode II fracture criterion including a restraint effect for cracks is verified to be applicable, where δ₁ and δ₃ are the maximum and minimum principal stresses, δ_t and δ_c are the tensile and compressive strengths and K_Ic and K_IIc are the mode I and II fracture toughness values, respectively. The above equation is similar in form to the Coulomb-Mohr criterion.Also a statistical correction for brittle fracture criteria under multiaxial stresses is discussed. By considering the allowable stress values for safe design, the specified minimum ultimate strengths corresponding to a survival probability of 99% at the 950 confidence level are presented.     

Irradiation effects on thermal shock resistance and fracture toughness of HTGR-graphite

This paper describes changes in the thermal shock resistance and the thermal shock fracture thoughness in addition to the usual mechanical properties including the diametral compressive strength and fracture toughness of four varieties of graphite for the high temperature gas-cooled reactor due to neutron irradiations of (1.6 2.3) × 10²¹ n/cm² (E > 0.18 MeV) at 600 850°C. These experiments are carried out by using small disk specimens which can be conveniently loaded into a capsule for irradiation in the Japanese Materials Testing Reactor. Both the thermal shock resistance and the thermal shock fracture toughness of graphites after irradiation decreased markedly despite of the increase in mechanical strength.     

Temperature-dependent change of serological specificity of Candida albicans NIH A-207 cells cultured in yeast extract-added Sabouraud liquid medium: disappearance of surface antigenic factors 4, 5, and 6 at high temperature

The cells of Candida albicans NIH A-207 strain (A-strain) cultivated in YSLM at high temperatures (37 and 40 degrees C) did not undergo agglutination with the factor sera 4, 5, and 6 in a commercially available factor serum kit, 'Candida Check', and formed a grape-like shape. The mannans isolated from the cells had lost their reactivity against the factor sera in ELISA. It was also revealed by 1H NMR analysis that the mannans contained neither a phosphate group nor a beta-1,2-linked mannopyranose unit, although these mannans increased the non-reducing terminal alpha-1,3-linked mannopyranose unit. The cells and the mannans prepared by cultivation at such high temperatures followed by 27 degrees C in the same medium entirely recovered the reactivity with the factor sera.     

Construction of T‐Motif‐Based DNA Nanostructures through Enzymatic Reactions

The most common way to fabricate DNA nanostructures is to mix individually synthesized DNA oligomers in one pot. However, if DNA nanostructures could be produced through enzymatic reactions, they could be applied in various environments, including in vivo. Herein, an enzymatic method developed to construct a DNA nanostructure from a simple motif called a T‐motif is reported. A long, repeated structure was replicated from a circular template by rolling circle amplification and then cleaved into T‐motif segments by restriction enzymes. These motifs have been successfully assembled into a ladder‐like nanostructure without purification or controlled annealing. This approach is widely applicable to constructing a variety of DNA nanostructures through enzymatic reactions.     

Antitumor Effects of Orally Administered Rare Sugar D-Allose in Bladder Cancer

D-allose is a rare sugar that has been reported to up-regulate thioredoxin-interacting protein (TXNIP) expression and affect the production of intracellular reactive oxygen species (ROS). However, the antitumor effect of D-allose is unknown. This study aimed to determine whether orally administered D-allose could be a candidate drug against bladder cancer (BC). To this end, BC cell lines were treated with varying concentrations of D-allose (10, 25, and 50 mM). Cell viability and intracellular ROS levels were assessed using cell viability assay and flow cytometry. TXNIP expression was evaluated using Western blotting. The antitumor effect of orally administered D-allose was assessed using a xenograft mouse model. D-allose reduced cell viability and induced intracellular ROS production in BC cells. Moreover, D-allose stimulated TXNIP expression in a dose-dependent manner. Co-treatment of D-allose and the antioxidant L-glutathione canceled the D-allose-induced reduction in cell viability and intracellular ROS elevation. Furthermore, oral administration of D-allose inhibited tumor growth without adverse effects (p < 0.05). Histopathological findings in tumor tissues showed that D-allose decreased the nuclear fission rate from 4.1 to 1.1% (p = 0.004). Oral administration of D-allose suppressed BC growth in a preclinical mouse model, possibly through up-regulation of TXNIP expression followed by an increase in intracellular ROS. Therefore, D-allose is a potential therapeutic compound for the treatment of BC.     

Real-time measurement and feedback control of ion temperature profile and toroidal rotation using fast CXRS system in JT-60U

A fast charge exchange recombination spectroscopy (CXRS) system has been developed for the real-time measurement and feedback control of ion temperature (T_i) profile and toroidal rotation velocity (V_t) in JT-60U. In order to control T_i and V_t in real-time, the charge exchange recombination spectroscopy with high time resolution, the real-time processor system, and the real-time control system have been developed. Utilizing this system, real-time control of the T_i gradient between r/a ∼ 0.25-0.5 has been demonstrated with neutral beams at high beta plasmas (normalized beta β_N ∼ 1.6-2.8). The strength of the internal transport barrier is controlled. Moreover, the real-time control of V_t has been demonstrated from counter (anti-parallel to the plasma current, I_p) to co (parallel to the I_p) direction. Then the behavior of edge localized mode (ELM) is changed by controlling the V_t.     

High‐Efficiency Motors Using Soft Magnetic Cores

We have developed a small and highly efficient axial gap motor whose stator core consists of a soft magnetic core. First, the loss sensitivities to various motor design parameters were evaluated by magnetic field analysis. Low sensitivity to the pole number and core dimensions ( ? 2.2 dB) was found for the total loss, which is the sum of the copper loss and the iron losses in the stator core and the rotor yoke. From this we concluded that to improve the motor efficiency, it is essential to reduce the iron loss in the rotor yoke and to minimize the other losses. With this in mind, a prototype axial gap motor was manufactured and tested. The motor has four poles and six slots. The motor is 123 mm in diameter and the axial length is 47 mm. The rotor has parallel magnetized magnets and a rotor yoke with magnetic steel sheets. The maximum measured rotor efficiency is 93%. This value roughly agrees with the maximum calculated efficiency of 95%.     

Human Gingival Integration-Free iPSCs; a Source for MSC-Like Cell

Mesenchymal stem cells (MSCs) are considered a potential autologous therapy for tissue engineering. The available procedures for MSC retrieval from patients are invasive, and their limited in vitro proliferation restricts their use in the treatment of damaged tissues. Therefore, it is important to establish an alternative and safe source of MSCs. The objective of this study was to demonstrate induced pluripotent stem cell (iPSC) generation from a combination of an accessible source tissue and an integration-free method; we also attempted the differentiation of iPSCs into MSC-like cells (MSLCs) for future autologous tissue engineering. iPSCs were derived from human gingival tissues, which are easily accessible in the field of dentistry, via the use of non-integrating episomal plasmids. Established iPSCs expressed embryonic stem (ES) cell-specific markers, as assessed by gene analysis and immunocytochemistry. Embryoid bodies and teratoma formation were formed from iPSCs, showing their capacity to differentiate into three germ layers. Furthermore, we were successful in differentiating iPSCs into MSLCs. They tested positively for their capacity of trilineage differentiation. Our results demonstrate that human gingival integration-free iPSCs, readily accessible stem cells generated using episomal plasmid vectors, are a promising source of MSLCs, which can be used in tissue regeneration.     

Substrate Recognition by a Dual-Function P450 Monooxygenase GfsF Involved in FD-891 Biosynthesis

GfsF is a multifunctional P450 monooxygenase that catalyzes epoxidation and subsequent hydroxylation in the biosynthesis of macrolide polyketide FD-891. Here, we describe the biochemical and structural analysis of GfsF. To obtain the structural basis of a dual-function reaction, we determined the crystal structure of ligand-free GfsF, which revealed GfsF to have a predominantly hydrophobic substrate binding pocket. The docking models, in conjunction with the results of the enzymatic assay with substrate analogues and site-directed mutagenesis suggested two distinct substrate binding modes for epoxidation and hydroxylation reactions, which explained how GfsF regulates the order of two oxidative reactions. These findings provide new insights into the reaction mechanism of multifunctional P450 monooxygenases.