[en] Lambda bacteriophage deoxyribonucleic acid (DNA) molecules stained with YOYO-1 were deposited and stretched on chemically modified Si(1 0 0) wafer and cover glass substrates. The Si(1 0 0) wafer with a natural oxide layer and the cover glass surface were first chemically modified by vapor phase chemisorption with mixed two organosilanes. DNA molecules were then aligned on the substrate surfaces by chemical and physical adsorption from an aqueous solution during molecular combing. The aligned DNA molecules were observed by Kelvin probe force microscopy and intermittent contact-mode atomic force microscopy (AFM) as well as fluorescence microscopy. Interaction between the stretched DNA molecules and the chemically modified Si(1 0 0) substrate surface was examined using these AFMs

[en] The effect of a surface water layer on DNA strands deposited on a substrate was studied by atomic force microscopy (AFM). DNA molecules were deposited and stretched on chemically modified glass coverslips by a molecular combing method. Lambda bacteriophage DNA molecules were aligned on the organosilane-modified substrate surfaces by chemical and physical adsorption during the molecular combing. The combed DNA molecules were observed in humidity-controlled air and in aqueous solutions by pulsed-force-mode AFM (PFM-AFM). Chemical modification of cantilevers with an Au-coated tip by organothiol compounds was also applied to DNA observation. Mapping adhesive forces in aqueous media was useful to discriminate chemically the DNA strands from the substrate surface. The results suggest that PFM-AFM can be used widely to image the stretched DNA molecules on the silane-modified substrates

[en] Defect sizing experiment was carried out by using the satellite pulse technique with ultrasonic method. The mode-changed pulses which come from both ends of the artificial flaws in the fabricated sample have been measured on the screen of cathod ray tube with both video mode and radio-frequency mode. The measured values of the flows deviate from the real values less than 10%. (author)

[en] About 100 fuel rods for TRIGA Mark III reactor to be loaded are tested by radiographic technique in KAERI with 170 KV and 2 MeV X-ray. Manufacturing conditions of the fuel pellets have been found to be irregular. Many of the pellets of fuel rods are cracked. Many spots are found on radiographic film, which are sure to be voids. (author)

[en] We demonstrate here by imaging successive surface reactions in self-assembled monolayers (SAMs) on Au(1 1 1) at molecular scale with a scanning tunneling microscope (STM): (i) SAM matrices formation with 1-octanethiol on Au(1 1 1) in ethanol, (ii) insertion of N-Fmoc-aminooctanethiol into the SAM matrices in ethanol, and (iii) removal of the Fmoc protecting group with tris(2-aminoethyl)amine (TAEA). The total reaction is formation of SAMs containing a small amount of NH₂ terminated molecules in the CH₃ terminated SAM matrices. After the reaction of the protecting group with TAEA, STM imaging revealed the decrease in heights of the inserted molecules on average. We attributed this observation to removal of the protecting group by taking account of a convolution of electronic and topographic contributions to observed STM heights. Apparent areas of the terminal groups, however, became larger on removal. The increase in the areas was attributed to water adsorption to the NH₂ terminal group under air

[en] Adhesive interaction between a tip and a sample surface was examined on a microscopic scale by pulsed-force-mode atomic force microscopy (PFM-AFM). The signal measured by monitoring pull-off force is influenced by various factors such as topography, elasticity, electrostatic charges, and adsorbed water on surfaces. Here, we focus on the topographic effects on the adhesive interaction. To clarify the topographic influence, the adhesive force measurement of a stretched DNA molecule with a smaller radius of curvature than that of a tip was carried out at low relative humidity (RH) with an alkanethiol-modified tip. The experimental conditions such as low RH and the use of the alkanethiol-modified tip were required to minimise the influence of water capillary force on hydrated DNA strands. The hydrophobic modification of a substrate surface was also important to minimise the adsorbed water effect. The DNA molecules were stretched on the substrate surfaces by an immobilisation process called a dynamic molecular combing method. The two-component vapour-phase surface modification with an alkylsilane mixed with a silane derivative containing an amino end group enhanced the DNA adsorption due to the electrostatic interaction. The experimental results for the topographic effects on the adhesive force mapping were reproducible

[en] 1. Fatigue Crack Sizing by Neutron, X-ray and Ultrasonics. For the purpose of sizing fatigue cracks, fatigue crack were measured by X-ray, ultrasonics and neutron beam. After fatigue cracks were formed in aluminum specimen, cracks measured by scale were 14.0 and 23.5mm and those by neutron radiography which was the closest values to those measured by scale, were 12.5 and 23.5mm. These results by neutron radiography were obtained by penetrating Cd(NO₃)₂-4H₂O as neutron absorbent. Therefore if proper penetrant is selected per specimen, neutron radiography is the most effective method to get good results of all nondestructive testing methods. 2. Discussion of Mechanized Ultrasonic Examination for RPV Outlet Nozzle-to-Shell Weld. Mechanized ultrasonic examination methods for the Kori unit 1 RPV outlet nozzle-to-shell weld were reviewed. The result from the preservice inspection and the second inservice inspection were compared with respect to the ultrasonic methods, calibration blocks, calibration methods and applied ASME codes. Ultrasonic attenuotion measurement was performed and calibration methods were simulated by using two calibration blocks. (Author)

[en] A study has been made on the correlation between ultrasonic attenuation and mechanical properties with different prior austenite grain size. It was found that ultrasonic attenuation is increased with increasing grain size, decreasing yield strength and increasing charpy impact energy value for ALSI 4140 steel. (Author)