Investigation of radiation-induced surface activation effect in austenitic stainless steel under ultraviolet and γ-ray irradiations

The radiation-induced surface activation (RISA) effect will be applied to the core design in supercritical light water reactor (SCWR) in order to achieve a high performance with excellent economy and safety. The purpose of the present study is to investigate the RISA effect in the candidate fuel cladding materials in SCWR such as PNC1520. The change of weldability due to RISA effect and the related microstructure analysis were performed in oxidized PNC1520 and 304 stainless steel with various oxidization periods. The phases contained in the surface oxide layer of the present specimen were identified as Fe₂CrO₄, γ-Fe₂O₃, and Fe₂O₃. The lifetime of 13.8 days for wettability improving factor was confirmed in the ultraviolet (UV) irradiation. Meanwhile, the long life of 13.8 days and short life of 0.8 days for wettability improving factors were identified in the γ-ray irradiation. Based on the fact that the band gap energies of Fe₂CrO₄, γ-Fe₂O₃, and Fe₂O₃ were, respectively, 2.1, 2.0, and 2.2 eV, and the photo energies of UV and γ-ray irradiation were 4.48 eV and 13.3 MeV, it is therefore clarified that the hydrophilization on the oxide layer is ascribed to the RISA effect.     

Measurement of liquid water content in cathode gas diffusion electrode of polymer electrolyte fuel cell

Water management in cathode gas diffusion electrode (GDE) of polymer electrolyte fuel cell (PEFC) is essential for high performance operation, because liquid water condensed in porous gas diffusion layer (GDL) and catalyst layer (CL) blocks oxygen transport to active reaction sites. In this study, the average liquid water content inside the cathode GDE of a low-temperature PEFC is experimentally and quantitatively estimated by the weight measurement, and the relationship between the water accumulation rate in the cathode GDE and the cell voltage is investigated. The liquid water behavior at the cathode is also visualized using an optical diagnostic, and the effects of operating conditions and GDL structures on the water transport in the cathode GDE are discussed. It is found that the liquid water content in the cathode GDE increases remarkably after starting the fuel cell operation due to the water production at the CL. At a high current density, the cell voltage drops suddenly after starting the operation in spite of a low water content in the cathode GDE. When the GDL thickness is increased, much water accumulates near the cathode CL and the fuel cell shuts down immediately after the operation. In the final section of this paper, the structure of cathode GDL that has several grooves for water removal is proposed to prevent water flooding and improve fuel cell performance. This groove structure is effective to promote the removal of the liquid water accumulated near the active catalyst sites.     

Identification of creep damage variable from A-parameter by a stochastic analysis

Identification of creep damage variable D of continuum damage theory from the metallographic A-parameter is discussed. By performing a stochastic analysis, A-parameter, defined as the observed fraction of cavitated grain boundaries on the observation plane, was first related to the cavity area fraction on the grain boundary facet planes. Based on the results of this analysis, the cavitation damage states of some engineering alloys were estimated by use of the data of the measured A-parameter. Finally, according to the usual interpretation of the damage variable D, specific D-A relations were derived. The validity and the utility of the proposed D-A relations, based on the test results of an engineering alloy, are discussed.     

Equilibrium and kinetic studies of selective adsorption and separation for strontium using DtBuCH18C6 loaded resin

A crown ether loaded resin was prepared by successive impregnation and fixing the 4′,4′(5″)-di(tert-butylcyclohexano)-18-crown-6 (DtBuCH18C6) and its molecule modifier, 1-dodecanol, onto the porous silica/polymer composite support (SiO₂-P particles). The characterization of DtBuCH18C6 loaded resin was examined by thermal gravimetry and differential thermal analysis and electron probe microanalysis. The adsorption behavior of Sr(II), Cs(I), Ru(III), Pd(II), La(III), Nd(III), Sm(III), Gd(III), Zr(IV), and Mo(VI) was investigated by the batch method. Furthermore, the column test for Sr (II) was performed. The batch experiments were carried out by varying the shaking times, HNO₃ concentration, and initial concentration of metal ions. A relatively large K _d value above 182 cm³/g for Sr(II) was obtained in the presence of 3 M HNO₃. In contrast, the K _d values of Cs(I), Ru(III), Pd(II), La(III), Nd(III), Sm(III), Gd(III), Zr(IV), and Mo(VI) were considerably lower than 10 cm³/g. The adsorption of Sr(II) was found to be controlled by chemisorption mechanism, and followed a Langmuir-type adsorption equation. The breakthrough curve of Sr(II) had S-shaped profile, and the elution percentage was estimated to be 99.9% by using the eluent of H₂O.     

Measurements of keV-neutron capture cross sections and capture gamma-ray spectra of 105Pd

The neutron capture cross sections and capture gamma-ray spectra of ¹⁰⁵Pd were measured in the region from 15 to 100 keV and at 585 keV. A neutron time-of-flight method was utilised with an anti-Compton NaI(Tl) spectrometer and a 1.5-ns pulsed neutron source by the ⁷Li(p,n)⁷Be reaction. The capture yields were obtained by applying a pulse-height weighting technique to the observed net capture gamma-ray pulse-height spectra. The capture cross sections of ¹⁰⁵Pd were derived with errors less than 5%, using the standard capture cross sections of ¹⁹⁷Au. The evaluated capture cross sections of JENDL-4.0 and ENDF/B-VII.1 were compared with the present results. The evaluations of JENDL-4.0 and ENDF/B-VII.1 were larger than the present results by 3%–15% in the region from 15 to 100 keV and at 585 keV. The capture gamma-ray spectra of ¹⁰⁵Pd were also derived by unfolding the observed net capture gamma-ray pulse-height spectra. The multiplicities of capture gamma rays of ¹⁰⁵Pd were obtained from the capture gamma-ray spectra.     

Regio- and stereoselective synthesis of carbocyclic 2'',3''-dideoxy-3''-fluoro nucleosides as potential antiviral agents

OBJECTIVE: To determine the prevalence of the symptom of urinary incontinence during athletic endeavors among a group of nulliparous, elite college varsity female athletes. METHODS: All women currently participating in varsity athletics at a large state university were asked to fill out a questionnaire about the occurrence of urinary incontinence while participating in their sport and during activities of daily life. One hundred forty-four of 156 eligible women (92%) responded. RESULTS: The mean age was 19.9 years, and all women were nulliparous. Overall, 40 athletes (28%) reported urine loss while participating in their sport. The proportions in different sports were: gymnastics 67%, basketball 66%, tennis 50%, field hockey 42%, track 29%, swimming 10%, volleyball 9%, softball 6%, and golf 0%. Two-thirds of the women who noted urine loss during athletics were incontinent more often than rarely. There were no statistically significant relations between incontinence and amenorrhea, weight, hormonal therapy, or duration of athletic activity. Activities most likely to provoke incontinence included jumping, high-impact landings, and running. Forty percent and 17% of the women first noted incontinence during their sport while in high school and junior high school, respectively. CONCLUSIONS: Incontinence during physical stresses is common in young, highly fit, nulliparous women. This suggests that there is a continence threshold which, when exceeded, can result in urine loss, even in the absence of known risk factors for incontinence.     

A case of ventricular septal perforation treated surgically with an infarction exclusion technique

We report an 85-year-old woman with postinfarction interventricular septal perforation. She underwent successful emergent surgical treatment by a slightly modified method based on David-Komeda's procedure. Perforation in this case occurred four days after acute myocardial infarction. Preoperative Qp/Qs was 2.58, and pulmonary artery pressure was 34/25 mmHg. The area of infarction was large, and the perforation was the linear type 2.5 cm long near the apex. A probe was not able to pass through the perforation due to its complicated configuration. A double Xenomedica patch was sutured on the left side of the interventricular septum without excising the infarcted area. The suture line was placed on healthy myocardium apart from the infarcted area. The Xenomedica patch was sandwiched between the closure line of the ventriculotomy. Four days after surgery, residual shunt was observed by echocardiogram, but this subsequently disappeared on the 17th postoperative day. The patient was discharged from our hospital on the 57th postoperative day, and is now doing quite well.     

Temperature dependence of birefringence and stress for natural rubber vulcanizates at strained state

The temperature dependence of stress and birefringence for natural rubber vulcanizates under medium and large deformation was measured for the processes of cooling, heating and re-cooling. In order to investigate the relation between the stress and crystal phase, the observed birefringence, Δt, was converted into the crystallinity, X_v, by the following equation:

$\text{X}{}_{\mathrm{<mtext>v</mtext>}}\text{=}\text{Δt?Δn}{}_{\mathrm{<mtext>a</mtext>}}\text{°f}{}_{\mathrm{<mtext>a</mtext>}}\text{Δn}{}_{\mathrm{<mtext>c</mtext>}}\text{°f}{}_{\mathrm{<mtext>c</mtext>}}\text{?Δn}{}_{\mathrm{<mtext>a</mtext>}}\text{°f}{}_{\mathrm{<mtext>a</mtext>}}$

where Δn⁰_c, Δn⁰_a, f_a and f_c are the intrinsic birefringence of the crystal, that of the amorphous phase, the orientation factor of crystallites, and that of amorphous phase, respectively. The fusion of crystallites induced by the thermal crystallization resulted in the increasing contractile force, while the fusion of strain-induced crystallites induced the reduction of contractile force.     

Decomposition of Carbon Dioxide to Carbon with Active Wustite at 300°C

Active wustite (FeδO, with a δ value of 0.98) was prepared by keeping normal wustite (δ value of 0.94) in a N₂ atmosphere at 300°C for 10 min. This reaction is given by (4δ₂–3)Fe_δ1O→(4δ₁–3)Fe_δ2O + (δ₂–δ₁)Fe₃O₄ where δ₁= 0.94 and δ₂= 0.98. The equation indicates that the normal wustite undergoes eutectoid decomposition into active wustite and stoichiometric magnetite (Fe₃O₄). Carbon dioxide (1.013 × 10⁵ Pa) was almost completely (100%) decomposed into carbon (zero valence) by the active wustite at the low temperature of 300°C, which was associated with the transformation of the active wustite into the stoichiometric magnetite. The internal pressure of the reaction cell eventually became a vacuum.     

Improvement of Selectivity for Partial Hydrogenation of Benzene by Rare Earth Nitride Upon NH3 Treatment

For the liquid-phase partial hydrogenation of benzene at 483 K, the selectivity toward cyclohexene was greatly improved upon treating rare earth nitride with ammonia. For YbN obtained by thermal decomposition of Yb(NH₂)₂ at 1173 K, the selectivity of the NH₃-treated YbN was 75%, in contrast to nil for the untreated YbN.