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Notes: A material for thermally stable self-aligned silicide technologies has been developed using sequentially deposited Ti/Ta on polycrystalline silicon. At lower annealing temperatures below 1000 °C two separate phases were found by cross-sectional transmission electron microscopy to exist in the form of bilayer TiSi2/TaSi2. The formation of a ternary phase (TiTa)Si2 has been observed at a higher temperature of 1000 °C. Consequently, the ternary (TiTa)Si2 layer could be kept extremely flat, with a sheet resistance of 5 Ω/(D'Alembertian), even after 1000 °C, 30 min annealing. Cross-sectional transmission electron micrographs of the structure clearly reveal that no agglomeration occurs during the heat treatment.

Notes: Using metalorganic chemical vapor deposition assisted by a nitrogen radical irradiation generated by rf plasma, we have enhanced the quality and the step coverage of titanium nitride barrier metals for the contact holes with a high aspect ratio and a submicron radius. Electrical resistivity measurements show that the film resistivity improves by a factor of five as the proper nitrogen irradiation has been applied. The step coverage in a contact hole with 0.4 μm diam and 3:1 aspect ratio has been improved from 50% to 80% by applying nitrogen plasma, clearly demonstrating the effectiveness of this technique in the conformal deposition of barrier metals for the ultra-large scale integration. The incident nitrogen radical is believed to play several roles, such as the enhancement of surface migration rate of molecules and the reduction of the amount of hydrocarbon incorporating into the film during the deposition. © 1996 American Institute of Physics.

Notes: Oxygen diffusion/incorporation behaviors of TiN/Ti/Si structures after thermal annealing in nitrogen ambients have been studied by x-ray photoelectron spectroscopy and cross-sectional transmission electron microscopy measurements. At the interface between Ti and TiN, titanium dioxides, thermodynamically most stable, are formed as a consequence of grain boundary diffusion, while inside TiN layer the contents of TiO and Ti2O3 compounds increases as the annealing temperature increases. At the interface between Ti and Si, titanium silicide formation is observed in the samples annealed above 450 °C consuming a part of pure Ti layer. One thing to note is that a severe blistering is observed in a sample annealed at 600 °C, probably caused by the difference of thermal expansion coefficients between TiSi2 and TiO2.

Notes: The atomic layer deposition technique has been applied to the growth of Al2O3 thin films on the substrates of Si(100), 100-nm-thick SiO2 covered Si(100) [SiO2/Si(100)], and 90-nm-thick TiN covered SiO2/Si(100). The growth rate of Al2O3 films was 0.19 nm/cycle and identical for all substrates employed under the surface controlled process. However, the optical properties of Al2O3 films were significantly affected by different substrates. The average interband-oscillator energy and refractive index parameter were determined to be 3.330 eV and 2.992×10−14 eV m2 for Al2O3 film grown on Si(100), while those for the film grown on SiO2/Si(100) were 4.492 eV and 2.074×10−14 eV m2, respectively. © 1997 American Institute of Physics.

Notes: Background In most epidemiological survey studies, only subjective symptoms and past medical history of asthma have been used as diagnostic criteria. Even though a questionnaire survey can be performed in a large population study at low cost, limitations such as lack of objectivity and poor predictability in non-specific bronchial hyperresponsiveness cannot be avoided.Objectives The purpose of this study was to elucidate the prevalence of current asthma based on questionnaires and methacholine bronchial provocation test, and the prevalence of atopy in Korea.Methods We performed modified ATS respiratory questionnaires and allergen skin-prick test with 10 common inhalant allergens among 3219 subjects aged 7–19 years in Seoul and a rural part of a small city, Chungju in Korea. Methacholine bronchial provocation tests were also performed among those who had asthma symptoms according to the questionnaire. The criteria of asthma was presence of both asthma symptoms and non-specific bronchial hyperresponsiveness. Atopy was defined as when an allergen induced weal size is same or larger than that caused by histamine.Results The prevalence of asthma based on questionnaires and methacholine bronchial provocation tests was 4.6%, while the prevalence of wheeze was 8.2% and 19.3% of total population complained of one or more respiratory symptoms related to asthma on the questionnaires. There was no significant difference according to age, sex and living area. The mean prevalence of atopy was 35.0% and the most common allergens were Dermatophagoides farinae (30.9%), Dermatophagoides pteronyssinus (27.5%), cat fur (20.4%) and cockroach (11.8%). The atopy prevalence in Chungju area was higher than that in Seoul and males showed a higher prevalence than females. The asthma prevalence was higher among atopies (6.8%) than among non-atopies (2.7%). None of questionnaire items were enough to predict the presence of bronchial hyperresponsiveness in terms of sensitivity, specificity and positive predictive value.Conclusion The prevalence rate of current asthma in Korea was 4.6% and the prevalence rate of atopy in Korea was 35.0%. Questionnaire-based surveys are not enough to predict the actual prevalence of asthma.

Notes: This study aimed to determine whether a preceding airway response to one allergen leads to priming of the airway responses to another allergen. Twelve asthmatic children who had positive prick tests to two allergens, Dermatophagoides pteronyssinus (D.p.) and German cockroach (CR), participated in a randomized, placebo-controlled crossover study. We performed two consecutive inhalation challenges, D.p. challenge being followed 48 h later by CR challenge. The effect of initial (D.p.) challenge on the early and late airway responses to the subsequent (CR) challenge (CR2) was examined by comparing the responses with those to CR challenge preceded by sham challenge (CR1). The geometric mean PD20 of CR allergen in the CR2 was 2.8 BU (breath unit) (range of 1 SD; 0.77-10.4), which was 12.0-fold less than that (33.7 BU, 10.8-105.2) in the CR1. The administration of a 6.1–fold less dose (8.9 BU, 2.7-28.8) in the CR2 than hi the CR1 (54.5 BU, 44.1-69.3) provoked a similar degree of late-phase reactions (18.7±7.3% vs 15.8 ± 9.6%). Our data indicated that the early- and late-phase reactions to CR challenge were augmented by the preceding reaction to D.p. This suggests that a preceding airway response to one allergen may lead to priming, with enhancement of the early and late airway responses to the subsequent challenge with another allergen.

Notes: Austenitic stainless components used in nuclear fusion reactors must be capable of maintaining reasonable mechanical properties to thermal ageing caused by welding and in-service. Recently, high-nitrogen (High-N) austenitic stainless steels (SS) are receiving increased attention because of their strength advantages, but they have been found to be susceptible to dichromium nitride (Cr2N) precipitation during thermal exposure at 823–1073 K. The susceptibility to sensitisation at thermal ageing temperature for high-N austenitic SS is examined using the single-loop electrochemical potentiokinetic reactivation (EPR) test. High-N SS were found to be susceptible to sensitisation caused by grain boundary precipitation of Cr2N, with the degree of sensitisation increasing systematically with ageing time and temperature. In particular, it was found that the precipitates, which effected sensitisation, were changed from carbides (M23C6) to nitrides (Cr2N) with increasing ageing time and temperature. The deterioration of mechanical properties associated with thermal ageing in high-N SS was investigated by a small punch (SP) test using miniature specimens at cryogenic temperatures. Results indicated that the degradation of mechanical properties in this alloy was caused by a decrease of cohesive strength resulting from carbides (Cr23C6) and nitrides (Cr2N) precipitated in grain boundaries.

Notes: Proton pump inhibitor-based triple therapies are recommended as the first-line treatment for Helicobacter pylori eradication.〈section xml:id="abs1-2"〉〈title type="main"〉Aim:To evaluate the efficacies of low-dose clarithromycin triple therapy and tinidazole-containing triple therapy in a metronidazole resistance prevalent area and to compare the efficacies with standard triple therapy.〈section xml:id="abs1-3"〉〈title type="main"〉Methods:In a randomized, multicentre, prospective study, a total of 352 patients with duodenal ulcer or non-ulcer dyspepsia were randomly divided into three groups according to the administered regimen: OAC250 group (omeprazole, 20 mg, amoxicillin, 1000 mg, and clarithromycin, 250 mg), OAC500 group (omeprazole, 20 mg, amoxicillin, 1000 mg, and clarithromycin, 500 mg) and OTC group (omeprazole, 20 mg, tinidazole, 500 mg, and clarithromycin, 500 mg). The three groups received each regimen twice daily for 7 days. Upper gastrointestinal endoscopy was performed before and 4 weeks after treatment. H. pylori status was determined by rapid urease test and 13C urea breath test.〈section xml:id="abs1-4"〉〈title type="main"〉Results:The eradication rates in the OAC250, OAC500 and OTC groups were 76.2%, 65.7% and 64.8% (95% confidence interval: 67.9–84.4%, 56.7–74.8% and 55.7–73.9%), respectively, by intention-to-treat analysis (P=0.149) and 92.8%, 87.2% and 84.1% (95% confidence interval: 84.4–97.3%, 77.9–93.8% and 73.9–91.2%), respectively, by per protocol analysis (P=0.088). All regimens were well tolerated and compliance was excellent.〈section xml:id="abs1-5"〉〈title type="main"〉Conclusions:Both low-dose clarithromycin triple therapy and tinidazole-containing triple therapy are effective and safe regimens for H. pylori eradication.