Measurement of large negative reactivity of an accelerator-driven system in the Kyoto University Critical Assembly

Large negative reactivity of a subcritical system driven by a pulsed 14 MeV neutron source has been measured in the Kyoto University Critical Assembly. The subcriticality of the accelerator-driven system (ADS) ranged in effective multiplication factor roughly from 0.98 to 0.92, which corresponded to an operational range of an actual ADS proposed by Japan Atomic Energy Agency. As the measurement technique, pulsed neutron method, power spectral analysis for pulsed neutron source, accelerator-beam trip method were employed. From neutron count decay data obtained by the pulsed neutron experiment, not only the prompt-neutron decay constant of fundamental mode but also a higher spatial mode could be derived. The subcriticality was also determined from the fundamental decay constant. The measured cross-power spectral density consisted of a familiar correlated reactor-noise component and many uncorrelated delta-function-like peaks at the integral multiple of pulse repetition frequency. The fundamental prompt-neutron decay constant, i.e., the subcriticality determined from the latter uncorrelated peaks was consistent with that obtained by the above pulsed neutron experiment. However, the magnitude of the former correlated component was reduced with an increase in the subcriticality and eventually this component became almost white at deeply subcritical state ranging in the multiplication factor under 0.95. Consequently, the determination of the decay constant from the correlated component was impossible under such a subcritical state. As data analysis method for the beam trip experiment, both the conventional integral count method and the least-squares inverse kinetics method (LSIKM) were employed. The LSIKM analysis led to the consistent subcriticality with that obtained by the pulsed neutron experiment, while the integral count method significantly underestimated the subcriticality. This underestimation originated from a residual background count, which was maintained after the beam trip. The LSIKM was mostly not influenced by such a slight count rate.     

Allene as an alternative functional group for drug design: effect of C--C multiple bonds conjugated with quinazolines on the inhibition of EGFR tyrosine kinase

A series of allenic quinazolines were synthesized as receptor tyrosine kinase inhibitors by using a simple protocol for palladium-catalyzed allene transformation. Among the compounds synthesized, two allenic 4-anilinoquinazolines selectively suppressed epidermal growth factor receptor (EGFR) tyrosine kinase activity in vitro. According to immunoblot analysis, the allenic quinazolines inhibited the EGF-mediated phosphorylation of EGFR and its downstream kinases in A431 cells. Furthermore, one of these allenic quinazolines decreased the proliferation of A431 cells through the induction of cell-cycle arrest and apoptosis.     

Steric Effect on the Catalytic Performance of the Selective Oxidation of Alcohols Over Novel Crystalline Mo–V–O Oxide

The Mo–V–O crystalline oxide with novel pore structure and consisting uniform six- and seven-member rings on the a–b plane is investigated for the selective oxidation of alcohols of different steric hindrance in liquid phase. The research target is to correlate catalytic activity with the pore structure of the crystal. Specially, substituted pyridines are employed as probe molecules to study poison effect which is closely related to the steric hindrance. As a result, the oxidation of benzyl alcohol, 1-hexanol and cyclohexanol produces aldehydes or ketones as main products. The oxidation of substrates with methyl groups on the carbon next to alcohol group mainly affords dehydrated products as olefins. The catalytic results with adding substituted pyridines in the oxidation of benzyl alcohol, 1-hexanol and 2-hexanol suggest that the active sites are located around the pore area, and are reachable by pyridine, not by substituted pyridines, such as 2-methylpyridine, 2-ethylpyridine and 2, 6-dimethylpyridine. Competitive adsorption on active sites between pyridine and benzyl alcohol remarkably decreases catalytic activity, which 2, 6-dimethylpyridine affects slightly. We have discussed that the adsorption-activation model of substrate is greatly dependent on its steric hindrance.     

Microstructural evolution and mechanical property in dual two-phase intermetallic alloys composed of geometrically close-packed Ni3 X (X: Al and V) containing Nb

Dual two-phase intermetallic alloys composed of geometrically close-packed (GCP) structures of Ni₃Al (L1₂) and Ni₃V (D0₂₂) containing Nb were investigated in terms of microstructural evolution during low-temperature annealing (aging) and the related mechanical properties. The eutectoid region, i.e. the prior Al phase (Ni solid solution) is composed of the lamellar-like structure consisting of Ni₃Al (L1₂) and Ni₃V (D0₂₂) even at an early aging stage, and then coarsen with increasing aging time. The lamellar-like structure tend to align along direction and on {001} plane in the prior A1 phase (or the L1₂ phase). In a wide range of temperature, the dual two-phase intermetallic alloys showed high yield and tensile strength, and also reasonable tensile ductility, accompanied with ductile fracture mode. The observed mechanical properties were less sensitive to the microstructural evolution during low-temperature annealing (aging), meaning that the present dual two-phase intermetallic alloy is promising for a new type of high-temperature structural material.     

Solid state NMR analysis of poly(L‐lactide) random copolymer with poly(ε‐caprolactone) and its reactive extrusion process

A random copolymer based on poly(L ‐lactide) (PLA) with poly(ε‐caprolactone) (PCL) was prepared and characterized by mechanical testing and solid state NMR, compared with a polymer blend. For a monofilament sample consisting of PLA/PCL random copolymer, there were negative correlations between the CL content and the mechanical properties: tensile strength, tensile elastic modulus, flexural rigidity, and flexural hysteresis decreased with increasing CL content. In contrast, the mechanical properties of the polymer blend were only slightly changed by addition of the CL unit. For the random copolymer, the addition of a small amount of CL reduced relaxation times, T₁C and T_1ρH, gradually. The T₁C and T_1ρH values correlated closely with the tensile elastic modulus and the tensile strength, respectively. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Conceptual core design of Advanced Recycling Reactor based on mature technologies

This paper presents about comprehensive investigations into Advanced Recycling Reactor (ARR) based on existing and/or mature technologies (called “Early ARR”), aiming transuranics (TRU) burning and considering harmonization of TRU burning capability, technology readiness, economy and safety. The ARR is a 500 MW_e (1180 MW_th) oxide fueled sodium cooled fast reactor, which the low core height of 70 cm and the large structure volume fraction with 1.0 mm of cladding thickness to tube wall have been chosen among 14 candidate concepts to reduce the TRU conversion ratio (CR) and the void reactivity, taking technology readiness into account. As a result of nuclear calculation, the ARR has TRU burning capability from 19 to 21 kg/TW_thh and is sustainable in recycling. And the ARR can accept several kinds of TRU; the LWR uranium oxide fuels, LWR-MOX used nuclear fuel, and TRU recycled in this fuel cycle and the ARR is also flexible in TRU management in ways that it can transform from TRU CR of 0.56 to breeding ratio (BR) of 1.03. In addition, it has been confirmed that the ARR core conforms to the set design requirements; the void reactivity, the maximum linear heat rate, and the shutdown margin of reactivity control system. It has been confirmed that the closed fuel cycle with the ARR plants of 180 GW_th will not release TRU outside and generate more electricity by 65% compared with the present nuclear power system in the US, curbing the risk of nuclear proliferation. Thus the study can conclude that the Early ARR is able to close nuclear fuel cycle, using mature technologies and has features of the sustainability in recycling, and the accommodation of almost all the TRU at present and in the future, and the flexibility in TRU management with breakeven core.     

Evaluation of theoretical critical angle including mass effects for channeling by computer simulation

The calculated critical angles using the theory included mass effects of Zheng et al. for the axial channeling of ion have been investigated by the computer simulations, making comparisons with the theory of Lindhard and the precise formula of Barrett’s numerical simulations. The computer simulations employing the ACOCT program code, which treats the atomic collisions three-dimensionally and is based on the binary collision approximation (BCA), were carried out for the channeling of He, Ne, Ar, Kr, Xe and Rn ions incident along the 〈1 0 0〉 axis in Al, Cu, Ag and Pt crystals. A slight dependence of the channeling critical angle on the atomic number of incident ion in the ACOCT results is in agreement with that in the calculated ones using the theory of mass effects. The average critical angles in the ACOCT results for the channeling of six rare gas ions are approximately 5.0/Z₂ times the magnitude of the theoretical critical angles with mass effects, where Z₂ is the atomic number of crystal atom. Besides, the results show that the calculated critical angles using the theory with mass effects are substantially larger than those using the theory of Lindhard, the Barrett’s formula and the formula by the ACOCT simulations for He ions impinging on Al, Cu, Ag and Pt crystals, and that the channeling critical angles in the ACOCT results agree well with those in the calculated ones using Barrett’s formula for 0.6-50 MeV He ions incident on Cu and Ag crystals and 5-50 MeV He ions impinging on Al and Pt crystals.     

Beneficial Effects of Supplementation of the Rare Sugar “D‐allulose” Against Hepatic Steatosis and Severe Obesity in Lepob/Lepob Mice

A rare sugar, D‐allulose (also called D‐psicose), has recently been applied as a food supplement in view of controlling diabetes and obesity in Japan. D‐allulose has been proven to have unique effects against hyperglycemia and hyperlipidemia in a number of studies using several species of rats and mice. However, the antiobesity effects of D‐allulose have not yet been assessed in Lep^ob/Lep^ob (ob/ob) mice. Therefore, this study explored the dietary supplemental effects of this sugar in leptin‐deficient ob/ob mice. Consequently, the subchronic ingestion of D‐allulose in ob/ob mice for 15 wk significantly decreased the body and liver weights, and the loss of body weight was involved in the reduction of the total fat mass, including abdominal visceral fat, and not fat‐free body mass, including muscle. Furthermore, D‐allulose improved hepatic steatosis, as evaluated using hepatic histological studies and MRI. In the normal mice, none of these parameters were influenced by the single or long‐term ingestion of D‐allulose. These results indicate that dietary supplementation of D‐allulose especially influences postprandial hyperglycemia and obesity‐related hepatic steatosis, without exercise therapy or dietary restriction. Therefore, D‐allulose may be useful as a supplement for preventing and improving obesity and obesity‐related disorders.     

Candidate Biomarkers for Genetic and Clinicopathological Diagnosis of Endometrial Cancer

The recent increase in the frequency of endometrial cancer has emphasized the need for accurate diagnosis and improved treatment. The current diagnosis is still based on conventional pathological indicators, such as clinical stage, tumor differentiation, invasion depth and vascular invasion. However, the genetic mechanisms underlying endometrial cancer have gradually been determined, due to developments in molecular biology, leading to the possibility of new methods of diagnosis and treatment planning. New candidate biomarkers for endometrial cancer include those for molecular epigenetic mutations, such as microRNAs. These biomarkers may permit earlier detection of endometrial cancer and prediction of outcomes and are likely to contribute to future personalized therapy for endometrial cancer.