Pellet compliance model based on out-of-pile simulation

The thermal and mechanical behavior of fuel rods is significantly influenced by the extent of their relocation and by compliance of the cracked pellets. Movement of the cracked pellet pieces towards the cladding results in softer pellets with crack voids which accommodate some fraction of the thermoelastic pellet deformation and make the pellet more compliant under the restraint of the cladding. It is difficult to model such a pellet compliance independently of experimental observations because the cracked pellet behavior is uncertain by nature.Electrically heated simulation of pellet-cladding mechanical interaction (PCMI) facilitates much quicker and more flexible experimentation than actual in-pile tests. Testing apparatus consists of the simulated fuel rod with hollow UO₂ pellets and a tungsten rod in the center, and a diameter measuring device including three pairs of diameter sensors. Test parameters include the pellet-cladding gap and the cladding thickness. Results show that rods with a smaller gap have a larger increasing rate of cladding diameter. This suggests that a group of cracked pellet pieces induced by thermal stress has an apparent compliance which increases with pellet-cladding gap. Results also show more sensitivity to cladding thickness than those calculated assuming pellets having intrinsic stiffness. This also suggests the compliant nature of cracked pellets.Such a compliant nature can almost be described by reducing the elasticity of the pellet. A simple pellet compliance model was obtained by fitting calculations with measurements to describe a cracked pellet as a uniform axisymmetric body with apparent elasticity.     

Detection of Helicobacter pylori associated antigen and heat shock protein 60 on follicular dendritic cells in the germinal centres of low grade B cell lymphoma of gastric mucosa associated lymphoid tissue (MALT)

AIMS: To investigate the localisation of Helicobacter pylori antigens and the expression of human heat shock proteins (HSP) in stomachs affected by MALT lymphoma. METHODS: Surgically resected stomachs from 24 patients with MALT lymphoma were immunostained with anti-H pylori rabbit antibodies (ORP-1 and ORP-2) and anti-human HSP60 mouse monoclonal antibodies (mAb) (LK-1 and LK-2). RESULTS: Follicular dendritic cells of germinal centres in the stomachs affected by MALT lymphoma were immunostained with anti-H pylori polyclonal antibodies and with anti-human HSP60 mAb, as were the epithelial cells. None of the lymph node samples reacted. CONCLUSIONS: Human HSP60, which cross reacts with anti-H pylori polyclonal antibodies, is often expressed on follicular dendritic cells in gastric MALT lymphoma tissues and may be aetiologically relevant to lymphomagenesis of MALT lymphoma.     

One-year monthly monitoring of Torque teno virus (TTV) in wastewater treatment plants in Japan

Torque teno virus (TTV) is a novel hepatitis virus which is considered to be transmitted by the fecal-oral route. Wastewater samples were collected monthly from eight wastewater treatment plants in Japan for 1 year, from July 2003 to June 2004, and tested for the presence of TTV by TaqMan PCR. TTV was detected in 97% (93/96) of influent samples, implying that TTV is epidemic in Japan. TTV was also isolated in 18% (17/96) of secondary effluent samples before chlorination and in 24% (23/95) of final effluent samples after chlorination. There was no significant difference between the concentration of total coliform in TTV-positive final effluents and that in TTV-negative final effluents, which indicates that total coliform cannot be used as an indicator of TTV. No TTV was detected in 24 effluents for reuse from two wastewater treatment plants using sand filtration and ozonation.     

螺旋锥齿轮齿面测量仪精度评定法

由齿面测量仪测得的螺旋锥齿轮的真实齿面形状是影响齿轮动态性能的重要因素之一,因此决定齿面测量结果可靠性的齿面测量仪本身精度的评定问题是一个重要的课题.介绍了一种利用球与圆柱组成的高精度样板仪来评价螺旋锥齿轮齿面测量仪精度的方法.并结合一种锥齿轮齿面测量仪的测量特点,介绍了测量领域的设置与标准测量数据的制作方法,最后给出了一组评定齿面测量仪精度的测量数据.该样板仪制作比较简单,精度高,利用它给螺旋锥齿轮齿面测量仪进行精度评定是一个非常实用、有效的方法.     

Separation selectivity of aqueous polyethylene glycol-based separation systems: DSC, LC and aqueous two-phase extraction studies

The distribution behavior of n-alcohols, ketones and nitroalkanes in aqueous liquid chromatography with a column packed with polyethylene glycol (PEG) gel, TSKgel Ether-250, was compared with that in aqueous two-phase systems (ATPSs) formed from PEG and Na₂SO₄ or (NH₄)₂SO₄. The plots of the distribution data obtained for the PEG gel system against those for the ATPS reveal that the separation selectivities exerted by the PEG gel system and the PEG-based ATPS are approximately the same. Differential scanning calorimetry studies on aqueous PEG solutions suggest that PEG polymer forms a hydration structure of which the composition is 50% (w/w) PEG or the hydration number per ethylene oxide is 2.4 and the separation selectivity of the PEG-water systems can be attributed to partition of solute compounds into the hydrated PEG polymer structure.     

Role of ComEA in DNA uptake during transformation of competent Bacillus subtilis

The role of the competence protein ComEA in DNA uptake during transformation of competent Bacillus subtilis was analyzed by lysed-protoplast transformation (LP transformation). A comEA deletion mutant was constructed by a fusion polymerase chain reaction. Transformants of the mutant were obtained by LP transformation at a frequency of 1.1 × 10(2) transformants per μg DNA, representing a low relative efficiency of transformation [RET (mutant/wild type)] of 2.7 × 10(-6). This implied an important role of the protein during DNA uptake. When analyzing LP transformation of comEA with a plasmid (5.7 kb), a similar RET (mutant/wild type) of 5.6 × 10(-5) was obtained. Following addition of DNA into the comEA mutant culture, the number of transformants increased at a rate of 0.5 transformants/min, which was very low compared with the wild-type (6.9×10(4) transformants/min). However, even in the comEA mutant, DNA uptake began immediately after addition of DNA. Using co-transformation analysis of the comEA mutant, short linkages at distances of 2-156 kb could be detected, but not long linkages at distances of 671-1662 kb. Taken together, the results indicate that ComEA plays an important role in the transfer of transforming DNA into the DNA channel and in controlling the rate of DNA uptake.     

Experimental studies of core flow fluctuations and neutron noise in a BWR

Using the instrumented fuel assemblies (IFA) installed in the Japan Power Demonstration Reactor (JPDR)-II core, fluctuations of the inlet and outlet channel flow rates were observed under both conditions of at-power operation and cold core flow circulation. The correlation analysis revealed that the flow fluctuations in any IFA channel showed almost uncorrelated cross-covariance function with other IFA channel flow. To explain the mechanism of the channel flow fluctuations, some hypothetical idea is introduced.     

Combined warfarin and antiplatelet therapy after St. Jude Medical valve replacement for mitral valve disease

OBJECTIVES: The clinical effect of combined warfarin and antiplatelet therapy on the incidence of stroke and postoperative complications after mitral (plus aortic) valve replacement was studied and compared with that observed with warfarin therapy alone. BACKGROUND: It has been reported that combined warfarin and antiplatelet therapy may be effective but may be associated with an increased hemorrhagic risk. Therefore, definite benefits of the treatment in patients with an implanted prosthetic valve have not been clearly documented. METHODS: Between January 1980 and December 1992, 195 patients with a St. Jude Medical valve at the mitral (plus aortic) position were assigned to receive treatment with either warfarin alone (125 patients) or warfarin plus antiplatelet agents (70 patients), such as dipyridamole (150 or 300 mg daily, 14 patients) or ticlopidine (200 or 400 mg daily, 56 patients). A minimal dose of aspirin (10 to 40 mg) was added (29 patients) if the maximal platelet aggregation rate by collagen was not reduced. The target thrombotest level was 10% to 20%. RESULTS: The two treatment groups were similar with regard to gender and age distribution. The number of patients with atrial fibrillation, left atrial thrombus, history of previous stroke, simultaneous aortic valve operation and previously performed valve procedures were comparable in the two groups. Actuarial survival rate at 10 years was 98.3 +/- 1.7% (mean +/- SD) in the warfarin plus antiplatelet group and 90.3 +/- 3.2% in the warfarin group (p < 0.05 at 1 and 9 to 12 years). The actuarial stroke-free rate at 10 years was 95.3 +/- 3.4% and 84.3 +/- 3.8%, respectively (p < 0.05 by the generalized Wilcoxon test). The actuarial complication-free rate at 10 years was 89.4 +/- 4.3% and 67.9 +/- 4.8%, respectively (p < 0.05 by the generalized Wilcoxon test). No hemorrhagic complications were seen in the warfarin plus antiplatelet group. CONCLUSIONS: The results strongly indicate the effectiveness and safety of combined warfarin plus antiplatelet treatment after St. Jude Medical valve replacement for mitral (plus aortic) valve disease.     

Lightning-induced voltage on an overhead wire dependent on groundconductivity

Lightning-induced voltage waveforms on an overhead wire are analyzed by solving the Telegrapher's equation, in combination with numerical calculations of electric fields from return stroke currents as inducing sources. Based on an equivalent circuit newly developed for an explanation of this method, the roles of the vertical and horizontal electric fields in generating the induced voltage are studied, respectively. By numerical calculations, it is pointed out that the crest value of the lightning-induced voltage waveform at the end of the line is greatly affected by the ground conductivity and the lightning striking points. The accuracy of the computed results is ensured by comparison with the experimental results obtained from a geometrical model on a finitely conducting ground     

Low loss fully reconfigurable wavelength-selective optical 1/spl times/N switch based on transversal filter configuration using silica-based planar lightwave circuit

A low loss wavelength-selective switch is proposed and demonstrated. The switch has a 1/spl times/4 transversal filter configuration that includes arrayed waveguide gratings and thermooptic phase shifters, and can route arbitrary wavelength input light to arbitrary outputs with no loss variation. We confirmed its operating principle and obtained an average loss of 2.7 dB and a worst extinction ratio of more than 20 dB.