Use of residual voltage for diagnosis of electrical power cables used in nuclear power stations

This paper describes the fundamental characteristics of the residual voltage and the relationship between irradiation dose and residual voltage in electric power cable used in nuclear power generating stations. The residual voltage of unirradiated cable increases with time, tending to saturate. The saturated value of residual voltage is nearly proportional to bias voltage. This result supports the residual voltage of cable being caused by depolarization. From theoretical and experimental investigations we found that the residual voltage is not influenced by cable size or length. This is an important merit of residual voltage as the nondestructive diagnosis. When dose is more than 500 kGy, the residual voltages exhibit a peak. As the irradiation dose is increased, the peak moves to shorter time. Therefore, we can determine the degree of radiation degradation from the location of the peak. © 1997 Scripta Technica, Inc. Electr Eng Jpn 119(2): 18–25, 1997     

Dusty Sheaths in Magnetized Plasmas

Parameters of self-consistent magnetized dusty sheaths are investigated using computer simulations of a temporal evolution of one-dimensional slab plasma with dust particles. The evolution is caused by a collection of electrons and ions by both a wall (electrode) and dust particles, which are initially immersed into plasma and distributed in front of the electrode. Obtained results show the existence of oscillations of a self-consistent potential in magnetized dusty sheaths including boundary potentials. Dust particles weaken magnetized sheaths and create additional sheaths close to a boundary of dust particles. The magnetic field does not influence on the dust particle charge.     

MiR-7-5p Is Involved in Ferroptosis Signaling and Radioresistance Thru the Generation of ROS in Radioresistant HeLa and SAS Cell Lines

In cancer therapy, radioresistance or chemoresistance cells are major problems. We established clinically relevant radioresistant (CRR) cells that can survive over 30 days after 2 Gy/day X-ray exposures. These cells also show resistance to anticancer agents and hydrogen peroxide (H₂O₂). We have previously demonstrated that all the CRR cells examined had up-regulated miR-7-5p and after miR-7-5p knockdown, they lost radioresistance. However, the mechanism of losing radioresistance remains to be elucidated. Therefore, we investigated the role of miR-7-5p in radioresistance by knockdown of miR-7-5p using CRR cells. As a result, knockdown of miR-7-5p increased reactive oxygen species (ROS), mitochondrial membrane potential, and intracellular Fe²⁺ amount. Furthermore, miR-7-5p knockdown results in the down-regulation of the iron storage gene expression such as ferritin, up-regulation of the ferroptosis marker ALOX12 gene expression, and increases of Liperfluo amount. H₂O₂ treatment after ALOX12 overexpression led to the enhancement of intracellular H₂O₂ amount and lipid peroxidation. By contrast, miR-7-5p knockdown seemed not to be involved in COX-2 and glycolysis signaling but affected the morphology of CRR cells. These results indicate that miR-7-5p control radioresistance via ROS generation that leads to ferroptosis.     

Lipids in human parotid saliva with regard to caries experience

It has been reported that saliva may play an important role in the prevention and development of enamel caries and that both lipids and protein contents in saliva may be relevant to this role. This study examined the lipid and protein levels in saliva from individuals differing in caries experience. Female subjects (20 to 21 years old) were used divided equally into two groups, caries-susceptible group (CSG) and caries-resistant group (CRG). Stimulated parotid saliva and stimulated whole saliva were collected from the subjects. After centrifugation, each saliva sample was analyzed for the concentrations of lipids and proteins and for the compositions of lipids and fatty acids. The lipid and protein contents in parotid saliva increased in proportion to increase of the flow rate. The lipid content was slightly correlated with the protein one (r = 0.33). Total lipid and protein concentrations were higher in the samples from CSG than those from CRG. The lipid composition was similar in the samples from the two groups; more than half in total lipids was neutral lipids, followed by glycolipids and phospholipids. Neutral lipids and free fatty acid and triacylglyceride concentrations were significantly higher in the samples from CSG than those from CRG (p<0.01 for each). Also stearic, linoleic and docosahexaenoic acids were significantly higher in the former group than the latter one (p<0.05 and p<0.01). In summary, the lipid concentrations in parotid saliva from caries susceptible subjects were higher than those from caries resistant ones, and the difference in fatty acid composition was detected between them. The variations in the lipid levels and fatty acid composition may be associated with those in caries development.     

Hydrothermal synthesis of TiO<Subscript>2</Subscript> nano-particles using novel water-soluble titanium complexes

Hydrothermal treatment of a series of water-soluble titanium complexes resulted in the formation of TiO₂. Rutile, anatase or a mixture of both can be synthesized by varying the ligands. The titania obtained was composed of nano-sized particles with large specific surface areas. These TiO₂ powders exhibited high photocatalytic activity for NO _x decomposition. In particular, they demonstrated higher activity than P25 (Degussa) under visible-light irradiation.     

Electron microscopy at a sub-50 pm resolution

An aberration-corrected electron microscope developed in CREST project has been applied for imaging atoms and clusters buried inside crystals. The resolution of the microscope in scanning transmission electron microscopy (STEM) has experimentally proved to be better than 47 pm by use of a cold-field emission gun at 300 kV. The high resolution has given an advantage for imaging light elements such as lithium atoms discriminating one by one. Moreover, a three-dimensional structure imaging has been demonstrated for dopant clusters by a sub-50 pm STEM, using its high depth resolution.     

Development of low cost production technologies for polycrystalline silicon solar cells

To develop a technology of forming grooves for low cost cell production, a multi-blade wheel grinding method was investigated. The process time of groove formation on the surface of 10 × 10 cm² polycrystalline silicon substrate was reduced to 30 s by a newly developed high-speed groove formation machine. Simultaneous formation of junction and anti-reflection coating by atmospheric pressure chemical vapor deposition (APCVD) technique was also investigated. For electrodes formation process, single firing method for both side electrodes made possible to simplify the firing process and to speed up from a conventional speed of 400 mm/min to 5000 mm/min.     

Isolation of a thermophile degrading poly(butylene succinate-co-butylene adipate)

A thermophile, strain 73, which degrades poly(butylene succinate-co-butylene adipate) (PBSA) film was isolated from 95 soil samples obtained from different locations by cultivation using an enrichment culture technique at 60 degrees C. At this temperature, the strain grew on PBSA and the dissolved total organic carbon (TOC) concentration in the medium changed according to the growth stage, i.e., after the TOC concentration rapidly reached the minimum, it increased rapidly until it reached a peak and then decreased thereafter. During cultivation, PBSA was almost eliminated and the solution viscosity of the residual PBSA decreased markedly. Gel permeation chromatograms of the residual PBSA showed a significant decrease in the main peak and the appearance of a new peak at the low molecular weight region. The strain was identified as Bacillus stearothermophilus, which has an optimum growth temperature of approximately 63 degrees C.     

Uric acid photo-oxidation assay: in vitro comparison of sunscreening agents

We present a new method to evaluate the photo-oxidative activity of sunscreening agents based on the photodynamic oxidation of uric acid. Uric acid was selected as the oxidant probe for its high reactivity to singlet oxygen and oxygen radicals, high sensitivity of detection using electrochemical (EC) techniques, low light absorptivity and high photochemical stability in the UVA/B region of interest, and stability to autoxidation. The method is demonstrated by the photodynamic oxidation of uric acid on co-irradiation with Rose Bengal, a highly efficient photosensitizing dye for the production of singlet oxygen (1O2). Using this assay we found that the relative photodynamic oxidation rates of UVB-absorbing sunscreens in 80% methanol on irradiation with >290 nm light decreased in the order 2-ethylhexyl 4-dimethylaminobenzoate (DMABA-2EH) > 2-ethylhexyl 4-methoxycinnamate (MCA-2EH) and the experimental sunscreens, 1-(1,1-dimethylethyl)-3-octanoyl-4,4-dimethyl- 1,4,5,6,-tetrahydropyridine (ICI-319) and 1-(2-methylpropyl)-3-propionyl-4,4-dimethyl-1,4,5,6-tetrahydropyridine (ICI-855). The relative photodynamic oxidation rates of UVA-absorbing sunscreens decreased in the order 4-tert-butyl-4'-methoxydibenzoylmethane (BMDBM) and 4-(2-propyl)benzophenone (PB) > 2-hydroxy-4'-methoxy-benzophenone (HMB) and 2,2'-dihydroxy-4-methoxybenzophenone (DHMB). We have confirmed the photodynamic activity of DMABA-2EH for the production of singlet oxygen (1O2) using electron paramagnetic resonance (EPR) spectroscopy and the reagent 2,2,6,6-tetramethyl-4-piperidone (4-oxo-TEMP). We failed to detect the photodynamic production of the oxyradicals, superoxide (O2.-) and hydroxyl radical (HO.) using N-tert-butyl-a-phenylnitrone (PBN) and 5,5-dimethyl-1-pyrrolidine-1-oxide (DMPO) as a result of photochemical interference caused by these spin-trapping reagents. The uric acid photo-oxidation assay was also used to compare the photodynamic reactivity of light-reflective, microfine oxides TiO2, ZnO and ZrO2 suspended in aqueous 80% methanol. All of the microfine oxides (uncoated) showed greater photodynamic reactivity in equimolar dispersion than did any of the organic UVA- and UVB-absorbing sunscreens in homogeneous solution. In this assay the photodynamic oxidation rates for the microfine oxides decreased in the order ZnO > TiO2 (anatase) > ZrO2 > TiO2 (rutile).