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Notes: 1. Pharmacological inhibition of nitric oxide (NO) synthesis is known to produce acute and chronic hypertension in many animal species, but the underlying mechanisms mediating the hypertension are not completely understood. In particular, the pathogenetic roles of sodium sensitivity and the sympathetic nervous system in this model of hypertension are controversial. The present study was designed to test the hypothesis that long-term administration of the NO synthesis inhibitor NG-nitro-L-arginine methyl ester (L-NAME) to male Sprague-Dawley rats would produce a sodium-sensitive hypertension and that the enhanced activity of the sympathetic nervous system in this type of hypertension contributes to the sodium sensitivity.2. NG-Nitro-L-arginine methyl ester was added to drinking fluid for 8 weeks at a concentration of 16 mg/dL. Rats received tap water for the first 4 weeks of the study and were then divided into two groups and placed on either a normal or high sodium intake (ingestion of either tap water or 0.9% NaCl, respectively). Awake systolic blood pressure was measured by the tail-cuff method every week. Urinary excretion rates of the stable NO metabolites and catecholamines during NO synthesis inhibition were examined.3. Long-term administration of L-NAME produced a marked and sustained elevation in arterial pressure without altering urine flow, or sodium excretion rate. NG-Nitro-L-arginine methyl ester-induced hypertension was accompanied by a decreased urinary excretion of the stable NO metabolites NO2– and NO3– and was aggravated when rats drank 0.9% NaCl in place of tap water. Urinary excretion of adrenaline and noradrenaline, but not dopamine, in L-NAME-treated rats increased significantly within the first week of the study compared with control rats. L-Arginine (2 g/dL in drinking fluid) completely reversed the elevation of arterial pressure as well as the decrease in urinary NO2– and NO3– excretion and the increased urinary excretion of catecholamines associated with L-NAME treatment by 3 weeks of concomitant administration.4. These results suggest that long-term inhibition of NO synthesis produces a sodium-sensitive hypertension and that changes in sympathetic nerve activity may, at least in part, contribute to the sodium sensitivity in this type of hypertension.

Notes: The EPR test, designed to examine of the susceptibility to nonuniform, primarily intergranular corrosion, ranks among the more successful testing technique developments relating to stainless steels and alloys. One of its numerous advantages is that it lends itself to non-destructive, on-site examination. EPR enjoyed wide expansion over the years since first conceived by Čihal in 1969. Recent EPR measurements tend to focus on (1) double and/or single loop EPR as a modern technique used to establish the resistance of stainless steels andalloys to intergranular corrosion; (2) detecting integranular corrosion (IGC) and intergranular stress corrosion cracking (IGSCC) susceptibility in alloy steels and nickel alloys for nuclear engineering applications; and (3) studies of grain boundary precipitation and other minute local changes to alloy composition and structure

Notes: The electronic properties of the interfacial oxide film formed on 304L stainless steel in high temperature water are investigated by contact electric resistance (CER) measurements. Tests are performed in pure water with a wide range of dissolved oxygen (DO) content at 200, 250, and 288°C. The electrochemical potential (ECP) moves in the noble direction and CER increases when increasing DO. Results show that DO content has a dominant effect on the electronic properties ofoxide film. The change of oxide film properties can also be attributed to the variation of the electrochemical potential, which is directly affected by DO content. Critical potentials exist for the formation and reduction of oxide films in high temperature water. Multiple steps are found for the reduction of oxide films due to de-aeration in 200, 250, and 288°C water, implying the presence of multiple-layer interfacial oxide films. The film reduction process is relatively slower than the film formation process. Present results show that even in high purity water, a moderate change of DOcontent can result in different surface conditions. Dissolved hydrogen has a moderate effect on interfacial surface films in deaerated water. In-situ monitoring of the oxide film properties by CER technique provides information on the interfacial reactions that are related to the SCC behavior of materials in high temperature water environments

Notes: A possible approach to describe the role of the environment in the phenomena behind crack initiation and crack propagation in stress corrosion cracking (SCC) is to assume that the transport of species through the oxide film on the material surface is one of the rate-controlling factors. The transport rates of ionic and electronic defects through the oxide film are, in addition to the environment,also affected by the stress and strain applied to the bulk material.In this paper, the surface oxide film formed on AISI 316L steel in slow strain rate tests (SSRT) in simulated BWR condition has been analyzed by using Electron Spectroscopy for Chemical Analysis (ESCA). The obtained film composition and structure have been combined with in-situ contact electric resistance (CER) measurements in order to evaluate the changes in oxide film electric properties during straining in the above environment. The results show that oxide film resistance of the strained part exhibits a maximum at around 2% of strain, which seems to correlate with a maximum in the Cr(III) concentration in the inner layer of the oxide. The implications of these results to SCC are discussed based on Mixed-Conduction Model (MCM)

Notes: Environmentally assisted cracking (EAC) consists of two distinct events viz., i) crack initiation and ii) crack propagation. On a smooth surface, the EAC initiates by the rupture or by the degradation of the surface film due to the combined action of stress and an electrochemical reaction of the materials with the environment. The mechanical properties of the surface oxide films are also important considerations when determining the susceptibility to EAC.In this research, Micro Raman Spectroscopy(MRS) was applied for in-situ oxides characterization and for in-situ measurements of the stress in oxide film formed on the surface of 304L stainless steel during the scratching electrode and the slow strain rate test (SSRT), respectively. The passive oxide film growth formed on the bare surface was continuously monitored by MRS as a function of time. For stress measurements, Cr〈sub〉〈/sub〉2O〈sub〉〈/sub〉3 was focused on and Raman shift at Cr〈sub〉〈/sub〉2O〈sub〉〈/sub〉3 peak of Raman spectrum was measured continuously. The strain rate was 8.2×10〈sup〉〈/sup〉-7 /sec. . In the initial stage ofSSRT, the Raman shift of surface film decreased gradually with strain. At 5% strain, the Raman shift of surface film increased rapidly to around the initial value of Raman shift. It is considered that the surface film was ruptured at this time. At 5% strain, the shift value of Raman peak of Cr〈sub〉〈/sub〉2O〈sub〉〈/sub〉3 reached to 5cm〈sup〉〈/sup〉-1. This value (5cm〈sup〉〈/sup〉-1) corresponds to 1.2GPa which value of tensile stress is calculated from reference data.These characteristics of oxide film will be implemented into the theoretical formulation of EAC and their implication to EAC growth rate will be discussed

Notes: Previously, we proposed stress corrosion cracking model on the basis of interaction of dislocation and hydrogen around a crack tip to predict discontinuous cleavage-like fracture during stress corrosion cracking (SCC) for ductile fcc alloys. Furthermore, we conducted numerical analyses using this proposed model. In the analysis, hydrogen was treated as a static cluster. However, actually, both of hydrogen and dislocations move with interaction each other. Therefore, in this paper, a physical model of dislocation and hydrogen dynamics with interaction was proposed. And the behavior of interaction between dynamic dislocations and hydrogen was investigated. On the basis of this analysis, the discontinuous cleavage-like fracture during SCC for ductile fcc alloys was clarified

Notes: A novel non-destructive inspection (NDI) technique that utilizes high-frequency signal transmission characteristics was developed as a more reliable, faster and cheaper NDI technique. This technique forms a transmission circuit that includes the specimen, and detects the signals generated by any surface breaking-defect.In this research, quantitative measurement of closed fatigue cracks was implemented via a newly developed probe. The greatest advantage of this technique is that there is no significant difference in detection of defects in either paramagnetic materials or in ferromagnetic materials. Therefore, the potential effects of corrosion, ferrite content, or deformation martensite on the measurement signals are minimized, and a better S/N ratio can be expected. This technique can also be used to measurethe size of defects in components, including welded components, and its detection sensitivity is less than 1 mm for surface breaking-defects

Notes: Primary water stress corrosion cracking (PWSCC) of Alloy 600 has been a great concern to the nuclear power industry. Reliable PWSCC growth rate data, especially at temperatures in the range of 290-330°C, of the alloy are required in order to evaluate the lifetime of power plant components. In this study, three tests were carried out in simulated pressurized water reactor (PWR) primary water at 325°C at different dissolved hydrogen (DH) concentrations using standard one-inch compact tension (1T-CT) specimens. The initiation and growth of cracks as well as insights into the different PWSCC mechanisms proposed in the literature were discussed. The experimental results show that the detrimental effects of hydrogen oncrack initiation and growth reached a maximum at a certain level of DH in water. Theexperimental results were explained in terms of changes in the stability of the surface oxide films under different DH levels. The experimental results also support the assumption that hydrogen absorption as a result of cathodic reactions within the metal plays a fundamental role in PWSCC