| 1. |
- Zhang, Qing, et al.
(author)
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Prevalence of Otitis Media With Effusion Among Children in Xi'an, China : A Randomized Survey in China's Mainland
- 2011
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In: Annals of Otology, Rhinology and Laryngology. - : SAGE Publications. - 0003-4894 .- 1943-572X. ; 120:9, s. 617-621
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Journal article (peer-reviewed)abstract
- Objectives: We sought to identify the prevalence of otitis media with effusion (OME) in urban Chinese children in Xi'an, China. Methods: Five kindergartens and 3 primary schools were randomly selected in the urban area of Xi'an. Screening otoscopic and tympanometric examinations were performed on 2,902 children (1,491 boys and 1,411 girls) 2 to 8 years of age. Children with an abnormal tympanogram and simultaneous otomicroscopic signs of effusion were given a diagnosis of OME. Results: The overall prevalence of OME was 4.3%. By age group, the prevalence was 14.0% in 2-year-olds, 8.3% in 3-year-olds, 5.0% in 4-year-olds, 4.9% in 5-year-olds, 2.8% in 6-year-olds, 1.7% in 7-year-olds, and 3.2% in 8-year-olds. The prevalence rate for OME was 4.7% for boys versus 3.9% for girls, and 3.0% in the right ear versus 2.7% in the left, showing no statistically significant difference between genders or between ear sides (p > 0.05). Conclusions: The prevalence of OME in urban areas of Xi'an is not high in comparison with that of the same age group in surrounding areas.
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| 2. |
- Bo, Tao, et al.
(author)
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Hexagonal Ti2B2 monolayer : a promising anode material offering high rate capability for Li-ion and Na-ion batteries
- 2018
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In: Physical Chemistry, Chemical Physics - PCCP. - : ROYAL SOC CHEMISTRY. - 1463-9076 .- 1463-9084. ; 20:34, s. 22168-22178
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Journal article (peer-reviewed)abstract
- Combining the first-principles density functional method and crystal structure prediction techniques, we report a series of hexagonal two-dimensional transition metal borides including Sc2B2, Ti2B2, V2B2, Cr2B2, Y2B2, Zr2B2, and Mo2B2. Their dynamic and thermal stabilities are testified by phonon and molecular dynamics simulations. We investigate the potential of the two-dimensional Ti2B2 monolayer as an anode material for Li-ion and Na-ion batteries. The Ti2B2 monolayer possesses high theoretical specific capacities of 456 and 342 mA h g(-1) for Li and Na, respectively. The very high Li/Na diffusivity with an ultralow energy barrier of 0.017/0.008 eV indicates an excellent charge-discharge capability. In addition, good electronic conductivity during the whole lithiation process is found by electronic structure calculations. The very small change in volume after the adsorption of one, two, and three layers of Li and Na ions indicates that the Ti2B2 monolayer is robust. These results highlight the suitability of Ti2B2 monolayer as well as the other two-dimensional transition metal borides as excellent anode materials for both Li-ion and Na-ion batteries.
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| 3. |
- Liu, Peng-Fei, et al.
(author)
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First-principles calculations of the ultralow thermal conductivity in two-dimensional group-IV selenides
- 2018
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In: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 98:23
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Journal article (peer-reviewed)abstract
- Through first-principles calculations, we report on the phonon-limited transport properties of two-dimensional (2D) hexagonal MSe (M = Ge, Sn, and Pb) compounds, which can be seen as a new family of 2D group-IV selenides established by the isovalent substitutions of germanium and tellurium in layered Ge-4 Se-3 Te phase [Angew. Chem. Inter. Edit. 56 10204 (2017)]. We find that 2D PbSe exhibits low values of sound velocity (800-2030 m/s), large Gruneisen parameters (similar to 1.93), low-lying optical modes (similar to 20.02 cm(-1)), and strong optical-acoustic phonon coupling. These intrinsic properties mainly stem from strong phonon anharmonicity, which greatly suppress the phonon transport and therefore give rise to an ultralow thermal conductivity (similar to 0.26 W m(-1) K-1) for 2D PbSe at room temperature. Our studies may offer perspectives for applications of thermoelectricity and motivate further experimental efforts to synthesize MSe compounds.
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| 4. |
- Wang, Hui, et al.
(author)
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On the Structure of alpha-BiFeO3
- 2013
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In: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 52:5, s. 2388-2392
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Journal article (peer-reviewed)abstract
- Polycrystalline and monocrystalline alpha-BiFeO3 crystals have been synthesized by solid state reaction and flux growth method, respectively. X-ray, neutron, and electron diffraction techniques are used to study the crystallographic and magnetic structure of alpha-BiFeO3. The present data show that alpha-BiFeO3 crystallizes in space group PI with a = 0.563 17(1) nm, b = 0.563 84(1) nm, c = 0.563 70(1) nm, alpha = 59.33(1)degrees, beta = 59.35(1)degrees, gamma = 59.38(1)degrees, and the magnetic structure of alpha-BiFeO3 can be described by space group PI with magnetic modulation vector in reciprocal space q = 0.0045a* - 0.0045b*, which is the magnetic structure model proposed by I. Sosnowska(1) applied to the new PI crystal symmetry of alpha-BiFeO3
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