Band-gap bowing and p-type doping of (Zn, Mg, Be)O wide-gap semiconductor alloys: a first-principles study

Using a first-principles band-structure method and a special quasirandom structure (SQS) approach, we systematically calculate the band gap bowing parameters and \emph{p}-type doping properties of (Zn, Mg, Be)O related random ternary and quaternary alloys. We show that the bowing parameters for ZnBeO and MgBeO alloys are large and dependent on composition. This is due to the size difference and chemical mismatch between Be and Zn(Mg) atoms. We also demonstrate that adding a small amount of Be into MgO reduces the band gap indicating that the bowing parameter is larger than the band-gap difference. We select an ideal N atom with lower \emph{p} atomic energy level as dopant to perform \emph{p}-type doping of ZnBeO and ZnMgBeO alloys. For N doped in ZnBeO alloy, we show that the acceptor transition energies become shallower as the number of the nearest neighbor Be atoms increases. This is thought to be because of the reduction of \emph{p}-\emph{d} repulsion. The N$_{\rm{O}}$ acceptor transition energies are deep in the ZnMgBeO quaternary alloy lattice-matched to GaN substrate due to the lower valence band maximum. These decrease slightly as there are more nearest neighbor Mg atoms surrounding the N dopant. The important natural valence band alignment between ZnO, MgO, BeO, ZnBeO, and ZnMgBeO quaternary alloy is also investigated.Comment: 7 pages, 3 figure

Diagnostic accuracy of perfusion-weighted phase-resolved functional lung magnetic resonance imaging in patients with chronic pulmonary embolism

PurposeThis study aimed to evaluate the diagnostic performance of perfusion-weighted phase-resolved functional lung (PW-PREFUL) magnetic resonance imaging (MRI) in patients with chronic pulmonary embolism (CPE).Materials and methodsThis study included 86 patients with suspected chronic thromboembolic pulmonary hypertension (CTEPH), who underwent PREFUL MRI and ventilation/perfusion (V/Q) single-photon emission computed tomography/computed tomography (SPECT/CT). PREFUL MRI was performed at 1.5 T using a balanced steady-state free precession sequence during free breathing. Color-coded PW images and quantitative parameters were obtained by postprocessing. Meanwhile, V/Q SPECT/CT imaging was performed as a reference standard. Hypoperfused areas in the lungs were scored for each lobe and segment using V/Q SPECT/CT images and PW-PREFUL MR images, respectively. Normalized perfusion (QN) and perfusion defect percentage (QDP) were calculated for all slices. For intra- and interobserver variability, the MRI images were analyzed 2 months after the first analysis by the same radiologist and another radiologist (11 years of lung MRI experience) blinded to the results of the first reader.ResultsOf the 86 enrolled patients, 77 met the inclusion criteria (36 diagnosed with CPE using V/Q SPECT/CT and 41 diagnosed with non-CPE etiology). For the PW-PREFUL MRI, the sensitivity, specificity, accuracy, and positive and negative predictive values for the diagnosis of CPE were 97, 95, 96, 95, and 98% at the patient level; 91, 94, 93, 91, and 94% at the lobe level, and 85, 94, 92, 88, and 94% at the segment level, respectively. The detection of segmental and subsegmental hypoperfusion using PW-PREFUL MRI revealed a moderate agreement with V/Q SPECT/CT (κ = 0.65; 95% confidence interval: 0.61–0.68). The quantitative results indicated that the QN was lower in the CPE group than in the non-CPE group [median score (interquartile range, IQR) 6.3 (2.8–9.2) vs. 13.0 (8.8–16.7), p < 0.001], and the QDP was higher [median score (IQR) 33.8 (15.7–51.7) vs. 2.2 (1.4–2.9), p < 0.001].ConclusionPREFUL MRI could be an alternative test to detect CPE without requiring breath-hold, contrast agents, or ionizing radiation

First-Principles Study of Magnetic Properties of 3dTransition Metals Doped in ZnO Nanowires

The defect formation energies of transition metals (Cr, Fe, and Ni) doped in the pseudo-H passivated ZnO nanowires and bulk are systematically investigated using first-principles methods. The general chemical trends of the nanowires are similar to those of the bulk. We also show that the formation energy increases as the diameter of the nanowire decreases, indicating that the doping of magnetic ions in the ZnO nanowire becomes more difficult with decreasing diameter. We also systematically calculate the ferromagnetic properties of transition metals doped in the ZnO nanowire and bulk, and find that Cr ions of the nanowire favor ferromagnetic state, which is consistent with the experimental results. We also find that the ferromagnetic coupling state of Cr is more stable in the nanowire than in the bulk, which may lead to a higherTcuseful for the nano-materials design of spintronics

ISIJ Int.

Blast furnace dust is a kind of solid waste that produced in the process of iron smelting and it contains large amount of Fe and non-ferrous metal elements. It's not only a very good Fe-contained resource, but also a very important non-ferrous metal resource. Application of blast furnace dust to RHF (Rotary Hearth Furnace) briquette is an effective and comprehensive utilization method. However the strength of the briquettes is low, therefore the application of binder to the briquette should be developed. In this study, physical and chemical characteristics of blast furnace dust were investigated firstly. And the experiments of different binder used in the briquettes were studied. Then the bonding mechanisms of binders were discussed. The experiment results showed that different binder has different bonding mechanism of the briquettes. According to the application effect of binders, it should be priority to use the composite binder, and the excellent collocation pattern is starch binder together with silicon-containing binder, such as sodium silicate.Blast furnace dust is a kind of solid waste that produced in the process of iron smelting and it contains large amount of Fe and non-ferrous metal elements. It's not only a very good Fe-contained resource, but also a very important non-ferrous metal resource. Application of blast furnace dust to RHF (Rotary Hearth Furnace) briquette is an effective and comprehensive utilization method. However the strength of the briquettes is low, therefore the application of binder to the briquette should be developed. In this study, physical and chemical characteristics of blast furnace dust were investigated firstly. And the experiments of different binder used in the briquettes were studied. Then the bonding mechanisms of binders were discussed. The experiment results showed that different binder has different bonding mechanism of the briquettes. According to the application effect of binders, it should be priority to use the composite binder, and the excellent collocation pattern is starch binder together with silicon-containing binder, such as sodium silicate