Diagnostic utility of fractional exhaled nitric oxide in prolonged and chronic cough according to atopic status

AbstractBackgroundCough-variant asthma (CVA) and cough-predominant asthma (CPA) are the major causes of persistent cough in Japan. The utility of fractional exhaled nitric oxide (FeNO) measurement in the differential diagnosis of persistent cough has been reported, but the influence of atopic status, which is associated with higher FeNO levels, on the diagnostic utility of FeNO has been unknown.MethodsWe retrospectively analyzed 105 non-smoking patients with prolonged and chronic cough that were not treated with corticosteroids and anti-leukotrienes.ResultsCPA was diagnosed in 37 patients, CVA in 40, and non-asthmatic cough (NAC) in 28. FeNO levels were significantly higher in the CPA [35.8 (7.0–317.9) ppb] and CVA [24.9 (3.1–156.0) ppb] groups than in the NAC group [18.2 (6.9–49.0) ppb] (p < 0.01 by Kruskal–Wallis test). The optimal cut-off for distinguishing asthmatic cough (AC; CPA and CVA) from NAC was 29.2 ppb [area under the curve (AUC) 0.74, p < 0.01]. Ninety-one percent of subjects with FeNO levels ≥29.2 ppb had AC. Meanwhile, 40% of AC patients had FeNO levels <29.2 ppb. Stratified cut-off levels were 31.1 ppb (AUC 0.83) in atopic subjects vs. 19.9 ppb (AUC 0.65) in non-atopic subjects (p = 0.03 for AUC).ConclusionsAlthough high FeNO levels suggested the existence of AC, lower FeNO levels had limited diagnostic significance. Atopic status affects the utility of FeNO levels in the differential diagnosis of prolonged and chronic cough

Preventing hydrogen embrittlement in stainless steel by means of compressive stress induced by cavitation peening

In this paper, it has been demonstrated that compressive residual stress induced by cavitation peening which is one of the mechanical surface modification techniques can reduce invasion of the surface of austenitic stainless steel by hydrogen. Cavitation peening was done with employing a cavitating jet in air. The specimens were prepared with different processing time of cavitation peening. Then, stress measurement was performed using an X-ray diffraction analysis. After that, the surface was charged with hydrogen employing a cathodic charging method. Hydrogen content was evaluated by a thermal desorption analysis using a gas chromatography. From the obtained results, hydrogen content was reduced along with increase in compressive residual stress at surface. In particular hydrogen content became to 15% at processing time of 2 s/mm introducing compressive residual stress of 378 MPa. In short, cavitation peening can drastically prevent invasion by hydrogen

Movement of Dislocations in the Sub-Surface of a Polycrystalline Metal by Cavitation Peening Observed by Transmission Electron Microscopy

The impact produced when cavitation bubbles collapse can be utilized to modify surfaces in the same way as shot peening and it is called cavitation peening (CP). CP is one of a number of surface modification techniques used to improve the fatigue strength of metallic materials by introducing compressive residual stress. Although it has been shown by an X-ray diffraction method that CP decreases the micro-strain related to dislocations in the sub-surface of a polycrystalline material, the mechanism for this decrease is unclear. In this paper, the movement of dislocations by CP was observed using transmission electron microscopy (TEM)

Hydrogen-assisted crack propagation in α-iron during elasto-plastic fracture toughness tests

Elasto-plastic fracture toughness tests of a commercially pure iron were performed in air and in hydrogen gas at two different pressures. Some unique characteristics of hydrogen-enhanced cracking were exhibited at both the macroscopic and microscopic length scales, based on the observation of fracture surface, fracture plane, plasticity distribution and dislocation structure. The possible mechanisms responsible for the hydrogen-induced degradation of fracture toughness are discussed.acceptedVersio

Suppression of Fatigue Crack Propagation of Duralumin by Cavitation Peening

It was demonstrated in the present paper that cavitation peening which is one of the mechanical surface modification technique can suppress fatigue crack propagation in duralumin. The impacts produced when cavitation bubble collapses can be utilised for the mechanical surface modification technique in the same way as laser peening and shot peening, which is called “cavitation peening”. Cavitation peening employing a cavitating jet in water was used to treat the specimen made of duralumin Japanese Industrial Standards JIS A2017-T3. After introducing a notch, fatigue test was conducted by a load-controlled plate bending fatigue tester, which has been originally developed. The fatigue crack propagation behavior was evaluated and the relationship between the fatigue crack propagation rate versus stress intensity factor range was obtained. From the results, the fatigue crack propagation rate was drastically reduced by cavitation peening and the fatigue life of duralumin plate was extended 4.2 times by cavitation peening. In addition, the fatigue crack propagation can be suppressed by 88% in the stable crack propagation stage by cavitation peening

Multi-scale observation of hydrogen-induced, localized plastic deformation in fatigue-crack propagation in a pure iron

In order to study the influence of hydrogen on plastic deformation behavior in the vicinity of the fatigue crack-tip in a pure iron, a multi-scale observation technique was employed, comprising electron channeling contrast imaging (ECCI), electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM). The analyses successfully demonstrated that hydrogen greatly reduces the dislocation structure evolution around the fracture path and localizes the plastic flow in the crack-tip region. Such clear evidence can reinforce the existing model in which this type of localized plasticity contributes to crack-growth acceleration in metals in hydrogen atmosphere, which has not yet been experimentally elucidated

Hydrogen-assisted fatigue crack propagation in a pure BCC iron. Part I: Intergranular crack propagation at relatively low stress intensities

The role of hydrogen on intergranular (IG) fracture in hydrogen-assisted fatigue crack growth (HAFCG) of a pure iron at low stress intensity was discussed in terms of the microscopic deformation structures near crack propagation paths. The main cause of IG fracture was assumed to be the hydrogen-enhanced dislocation structure evolution and subsequent microvoids formation along the grain boundaries. Additionally, the impact of such IG cracking on the macroscopic FCG rate was evaluated according to the dependency of IG fracture propensity on the hydrogen gas pressure. It was first demonstrated that the increased hydrogen pressure results in the larger area fraction of IG and corresponding faster FCG rate. Moreover, gaseous hydrogen environment also had a positive influence on the FCG rate due to the absence of oxygen and water vapor. The macroscopic crack propagation rate was controlled by the competition process of said positive and negative effects