Vertebral fracture severity assessment on anteroposterior radiographs with a new semi-quantitative technique.

We developed a new tool to assess the severity of osteoporotic vertebral fracture using radiographs of the spine. Our technique can be used in patient care by helping to stratify patients with osteoporotic vertebral fractures into appropriate treatment pathways. It can also be used for research purposes. PURPOSE: The aim of our study was to propose a semi-quantitative (SQ) grading scheme for osteoporotic vertebral fracture (OVF) on anteroposterior (AP) radiographs. METHODS: On AP radiographs, the vertebrae are divided into right and left halves, which are graded (A) vertical rectangle, (B) square, (C) traverse rectangle, and (D) trapezoid; whole vertebrae are graded (E) transverse band or (F) bow-tie. Type A and B were compared with normal and Genant SQ grade 1 OVF, Type C and D with grade 2 OVF, and Type E and F with grade 3 OVF. Spine AP radiographs and lateral radiographs of 50 females were assessed by AP radiographs SQ grading. After training, an experienced board-certified radiologist and a radiology trainee assessed the 50 AP radiographs. RESULTS: The height-to-width ratio of the half vertebrae varied 1.32-1.48. On lateral radiographs, 84 vertebrae of the 50 patients had OVFs (38 grade 1, 24 grade 2, and 22 grade 3). On AP radiographs, the radiologist correctly assigned 84.2%, 91.7%, and 77.2% and the trainee correctly assigned 68.4%, 79.2%, and 81.8% of grade 1, 2, and 3 OVFs, respectively. Compared with lateral radiographs, the radiologist had a weighted Kappa of 0.944 including normal vertebrae and 0.883 not including normal vertebrae, while the corresponding Kappa values for the trainee were 0.891 and 0.830, respectively. CONCLUSION: We propose a new semi-quantitative grading system for vertebral fracture severity assessment on AP spine radiographs.

Prediction of New Phase and Electrochemical Properties of Li2S2 for the Application of Li-S Batteries.

The intermediate product Li2S2 plays a pivotal role in the charge/discharge process of lithium-sulfur batteries. However, the structural configuration and relevant properties of Li2S2 are unclear. In this work, by using ab initio calculations, we present results of novel phases, average open circuit voltages ( Vocs), and electronic properties of the stable Li2S2. Two new Li2S2 phases are predicted: orthorhombic ( Cmca) and orthorhombic ( Immm) structures. The calculated Vocs of hexagonal ( P63/ mmc), orthorhombic ( Cmca), and orthorhombic ( Immm) are 3.91, 3.95, and 3.88 V, respectively. In particular, the calculated band gap of the Immm structure is about 0.225 eV, which is smaller than that of Li2S. The narrow band gap of Li2S2 derives from the electronic lump between the Li s state and S 3p state for the orthorhombic structure. Therefore, the electronic properties of Li2S2 are markedly influenced by the structural configuration.

Insight into the electronic and mechanical properties of novel TMCrSi ternary silicides from first-principles calculations.

Transition metal silicides (TMSis) are attractive advanced functional materials due to their low electronic resistivity, high melting-point, excellent mechanical properties and thermal stability. However, the overall performances of binary silicides are not satisfactory enough to meet the requirements of many commercial applications. To overcome this problem, utilizing ternary silicide is a good path to adjust the balance between the overall performances because metallic bond plays a key role in electronic properties. The TM-Si bond enhances the strength, while the alloying element (Cr) can effectively improve the oxidation and corrosion resistances. Therefore, we report the results of electronic, mechanical and thermodynamic properties of stable TMCrSi ternary silicides by using first-principles calculations. First, we found that TMCrSi ternary silicides are dynamically stable based on the phonon dispersion curves. Second, the constructed ternary silicides exhibit better electronic properties because of the formation of TM-Cr metallic bond. Importantly, these ternary silicides not only show high strength, but also have better ductility. Additionally, the Debye temperature and heat capacity of TMCrSi ternary silicides are discussed. Finally, through our study, we propose that TMCrSi ternary silicides are promising functional materials with potential applications in aerospace, microelectronic and energy storage systems.

Probing the balance between ductility and strength: transition metal silicides.

The adjustment of the balance between strength and ductility is still a great challenge for ultrahigh temperature materials. Essentially, the strength depends on the valence electron density of transition metals and the bond strength of chemical bonding. However, the ductility of a solid is mainly determined by the symmetrical slips and crystal structure. Based on the above design principles, we apply first-principles calculations to investigate the structure, elastic properties and brittle-or-ductile behavior of TM3Sis with a cubic structure. Two new TM3Si structures: Ti3Si and W3Si (space group: Pm3[combining macron]n) are predicted. The calculated results show that W3Si exhibits strong volume deformation and shear deformation resistances in comparison to TM5Si3. In particular, W3Si also exhibits excellent ductility due to the symmetrical structure. The calculated electronic structure reveals that a high elastic modulus derives from the strong and symmetrical W-Si and W-W bonds. Therefore, we can control a crystal structure with symmetrical slips and choose a TM metal with a high valence electron density, to improve the correlation between ductility and strength.