Acoustic Radiation Force Impulse (ARFI) imaging is a novel ultrasound‐based elastography method that is integrated in a conventional ultrasound machine enabling the exact localization of ...measurement site. It might present an alternative method to transient elastography for the noninvasive assessment of liver fibrosis. At present, studies with small patient population have shown promising results. A systematic review and meta‐analysis of pooled patient data were performed to evaluate the overall performance of ARFI for the staging of liver fibrosis. Literature databases were searched up to 10/2010. The authors of the original publication were contacted, and the original patient data were requested. A meta‐analysis was performed using a random effect meta‐analytic method for diagnostic tests. In addition, available data comparing ARFI with FibroScan with the DeLong test were evaluated. Literature search yielded nine full‐paper publications evaluating ARFI while using liver biopsy as reference method. Original patient data were available from eight studies including 518 patients. The mean diagnostic accuracy of ARFI expressed as areas under ROC curves (AUROC) was 0.87 for the diagnosis of significant fibrosis (F ≥ 2), 0.91 for the diagnosis of severe fibrosis (F ≥ 3), and 0.93 for the diagnosis of cirrhosis. ARFI can be performed with good diagnostic accuracy for the noninvasive staging of liver fibrosis.
In order to establish a method for monitoring whether flashover occurs or not in a string of insulators based on leakage current waveforms and their frequency characteristics, the leakage current ...waveforms and the frequency characteristics of a string of 120-kN suspension insulators were investigated with artificial contamination tests and field tests. As a result, it was found that leakage current waveforms become nearly the symmetrical wave when strong local arcs occur; hence, the intensity of the odd order of harmonic components, e.g., 50, 150, and 250 Hz, is high. Furthermore, it was clarified that the transition of the leakage current waveforms until flashover occurs is classified into six stages and that a threshold exists in the magnitude of peak leakage current and prominent odd-order harmonic components by which the occurrence of flashover can be predicted.
In order to establish a method for monitoring contamination in insulators based on leakage current waveforms and their frequency characteristics, the leakage current waveforms and frequency ...characteristics of an artificially polluted 180 mm diameter cap and pin type insulator were investigated by the wet contaminant and the clean fog methods at fixed applied voltages. As a result it was found that leakage current waveforms become similar to the symmetrical wave when strong local arcs occur; hence, the intensity of the odd order of harmonic components, e.g. 50, 150, and 250 Hz, is high. Furthermore, it was clarified that the transition of the leakage current waveforms, until flashover occurs, is classified into six stages and that a threshold exists by which the occurrence of flashover can be predicted.
We present the chemical abundances of six stars in the halo stream Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST)-N1, a new kinematically selected substructure from LAMOST data, ...from high-resolution spectra obtained with the Subaru/High Dispersion Spectrograph. Atmospheric parameters were determined by an iterative procedure based on spectroscopic analysis. Abundances of 11 elements, including elements (Mg, Ca, Ti), odd-Z light elements (Na), iron-peak elements (Sc, Cr, Mn, Fe, Ni), and neutron-capture elements (Y, Ba), are measured by local thermodynamic equilibrium analysis procedures. Fe/H of the six stars ranges from −1.5 to −0.66. The abundance patterns of elements show a similar trend to those of low- stars in Nissen et al. and over 0.1 dex lower than those of Galactic field stars. The Sc, Cr, Mn, and Ni abundances of these six stars exhibit a positive trend with increasing iron abundance, with varying gradients. In addition, abundance distribution between Na/Fe and Ni/Fe and between that of Ba/Y and Fe/H of these six stars is different from both Galactic stars and the known dwarf galaxies. Our results suggest that LAMOST-N1 might be a relic of a system with slower chemical evolutions than the Milky Way.
We present extensive sets of stellar models for ranges 0.8–9.0 M⊙ in mass and −5 ≤Fe/H≤− 2 and Z= 0 in metallicity. The present work focuses on the evolutionary characteristics of hydrogen mixing ...into the helium-flash convective zones during the core and shell helium flashes that occur for models with Fe/H≲− 2.5. Evolution is followed from the zero-age main sequence to the thermally pulsating asymptotic giant branch (AGB) phase, including hydrogen engulfment by helium-flash convection during the red giant branch (RGB) or AGB phases. Various types of mixing episodes exist, with regard to how hydrogen mixing sets in and how it affects the final abundances at the surface. In particular, we find hydrogen ingestion events without dredge-ups that enable repeated neutron-capture nucleosynthesis in the helium-flash convective zones with 13 C (α, n)16 O as the neutron source. For Z= 0, the mixing and dredge-up processes vary with the initial mass, which results in different final abundances at the surface. We investigate the occurrence of such events for various initial mass and metallicity values to find the metallicity dependence for helium-flash-driven deep mixing (He-FDDM) and also for third dredge-up events. In our models, we find He-FDDM for M≤ 3 M⊙ for Z= 0 and for M≲ 2 M⊙ for −5 ≤Fe/H≤− 3. However, the occurrence of the third dredge-up is limited to the mass range ∼ 1.5–5 M⊙ for Fe/H=− 3, a range that narrows with decreasing metallicity. This work also discusses the implications of the results of model computations for observations. We compare the abundance pattern of CNO abundances with that for observed metal-poor stars. The origins of the most iron-deficient stars are discussed by assuming that these stars are affected by binary mass transfer. We also point out the existence of a blue horizontal branch for −4 ≲Fe/H≲− 2.5.
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