Excitation of the n=4 Levels of He⁺ by the Impact of H⁺, He⁺ and He²⁺ Ions

The emission cross sections of Hell (4→3) 4686 Å line by the incident beams of 0.5-1.5 MeV H⁺, 1.0-2.5 MeV He⁺ and 1.0-2.0 MeV He²⁺ are studied. By measuring the lateral distribution of the light intensity, the excitation of He⁺ (n＝4) levels is found to be caused by direct collision. The emission cross section by the proton impact is due to the ″ionization process″ and shows an E⁻¹ dependence, while that by the helium ion impact is due to the “charge transfer process” as well as the “ionization process” and shows a steeper energy dependence

Excitation of Nitrogen Molecule by the Impact of 80-160 kev Proton

Light emission from nitrogen molecules excited by the impact of 80-160 kev protons was studied over a wave length ranging from 3300 to 5400 Å. The lateral distributions of the light intensities were also measured. From the target gas pressure dependence of the light intensities and their lateral distributions, it was shown that the state B²Σ⁺ᴜ of N⁺₂ was excited by a direct proton collision, and that the state C³IIᵤ of N₂, having a singlet-triplet mixing, was excited by secondary processes

Evaluation and visualization of multiaxial fatigue behavior under random non-proportional loading condition

In cyclic multiaxial stress/strain condition under nonproportional loading in which principal direction of stress/strain are changed in a cycle, it becomes difficult to analyze stress/strain ranges because of complexity of multiaxial stress/strain states depending on time in cycles. In order to evaluate stress/strain simply and suitably under non-proportional loading, Itoh and Sakane have proposed a method called as IS-method and a strain parameter for life evaluation under non-proportional loading ??NP. In the method, 6-components of stress/strain are converted to an equivalent stress/strain indicating the amplitude and the direction of principal stress/strain as a function of time as well as an intensity of loading nonproportionality fNP. Based on IS-method, the authors also have developed a tool which enables to analyze multiaxial stress/strain condition with the nonproportionality of loading history and evaluate failure life under nonproportional multiaxial loading. The tool indicates the analyzed results on monitor and users can understand visually not only variation of the stress/strain conditions but also non-proportionality during the cycle, which helps the design of material strength

Influence of notch sensitivity and crack initiation site on low cycle fatigue life of notched components under multiaxial non-proportional loading

A series of strain controlled multiaxial low cycle fatigue (LCF) tests under proportional and non-proportional loading conditions have been conducted on notched specimens. Cylindrical bars of Al 6061 aluminum alloy and AISI 316L stainless steel with four values of stress concentration factors referred to the net section Kt,n were employed. The experimental results evidenced a reduction of fatigue life due to non-proportional loading. Furthermore, the crack initiation site has been detected to be moved from the notch tip in the case of steel for high values of notch radius under nonproportional loading. Stress concentration factor evaluated in the elastic field Kt,n has been included in the Itoh-Sakane parameter to evaluate the fatigue life, returning a general underestimation of fatigue life especially for high values of Kt,n. Material notch sensitivity and crack initiation position have been taken into account to further modify the model, improving the original results and showing a better assessment

Influence of Notch Sensitivity and Crack Initiation Site on Low Cycle Fatigue Life of Notched Components under Multiaxial Non-proportional Loading

A series of strain-controlled multiaxial low cycle fatigue (LCF) tests under proportional and non-proportional loading conditions have been conducted on notched specimens. Cylindrical bars of Al 6061 aluminum alloy and AISI 316L stainless steel with four values of stress concentration factors referred to the net section Kt,n were employed. The experimental results evidenced a reduction of fatigue life due to non-proportional loading. Furthermore, the crack initiation site has been detected to be moved from the notch tip in the case of steel for high values of notch radius under non-proportional loading. Stress concentration factor evaluated in the elastic field Kt,n has been included in the Itoh-Sakane parameter to evaluate the fatigue life, returning a general underestimation of fatigue life especially for high values of Kt,n. Material notch sensitivity and crack initiation position have been taken into account to further modify the model, improving the original results and showing a better assessment

Role of <em>COX-2</em> Promoter Methylation and <em>Helicobacter pylori</em> Infection in Impaired Gastric Ulcer Healing

Helicobacter pylori (H. pylori) infection causes aberrant DNA methylation of various genes in the gastric mucosa. Cyclooxygenases (COX) play a critical role in peptic ulcer development and healing. Human COX-2 has CpG islands (CGIs) in its promoter region, suggesting a possible epigenetic regulation. Here, we evaluated COX-2 promoter methylation in the gastric mucosa of patients with various gastric diseases and found that COX-2 methylation levels in the gastric mucosa were significantly increased in patients with H. pylori infection. We further investigated the roles of COX-2 during the healing of acetic acid-induced gastric ulcers in H. pylori-infected Mongolian gerbils (MGs). While COX-2 mRNA expression levels on the edges of acetic acid-induced gastric ulcers were significantly increased after ulcer induction in MGs in the absence of H. pylori, no such induction was observed in H. pylori-infected gastric mucosa. Cloning of the MG COX-2 gene revealed abundant CGIs in the promoter region. COX-2 mRNA expression in MG-derived gastric carcinoma MGC2 cells was significantly increased by addition of the demethylating agent 5-Aza-dC. Additionally, COX-2 methylation levels were higher in H. pylori-infected MG gastric mucosa than in control mucosa. These results indicated that epigenetic inhibition of COX-2 mRNA induced by H. pylori impairs gastric ulcer healing

Establishment of Monitoring System to Detect Single Copy DNA Included in One Genome but not in Another Using Representational Difference Analysis

Polyrnerase chain reaction (PCR) -coupled subtractive procedure, representa-tional difference analysis (RDA) , is an efficient method to find the differences between two complex genomes. RDA has been applied to detect genetic lesions in cancer, the identification of unknown pathogens from the genomes, and the isolation of polymorphic markers. However, characterization of various clones obtained by RDA is time consuming and laborious work, and it is of great impor-tance to monitor whether RDA really works. To establish a monitoring system to detect single copy target DNA, we studied whether RDA could detect four fragments of non-human DNA which were added in one genome but not in another. We were able to successfully detect the target DNAs which were mixed at the ratio of single and ten copies per haploid genome using RDA with some modification of the original protocol. We confirmed that RDA was sensi-tive and effective enough to detect such genetic lesions as occurred in cancer cells. The target DNA used in this model could be utilized as a positive control in other applications of RDA