Mechanical properties and the effect of metallic bonding on the hardness of transition-metal nitrides ( TiN , VN and CrN ) compounds are studied using the first-principles calculation. Present results show that these transition-metal nitrides are mechanically stable and the VN and CrN are ductile, whereas TiN is predicted to be brittle. Moreover, it is found that the high hardness of TiN , VN and CrN exhibits a remarkable decrease with transition-metal changed from Ti to Cr , and the metallic d–d interactions play important roles on determining the hardness of transition-metal nitrides.
Polymorphism exhibits different physicochemical properties, which can impact the bioavailability and bioactivity of solid drugs. This study focused on identifying the polymorphs of ginsenoside compound K (CK) and studying their different behaviors in pharmacokinetics (PK) and pharmacodynamics (PD). Four CK polymorphs (form I, II, III, and IV) from organic solvents were characterized by scanning electron microscope (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and powder X-ray diffraction (PXRD). A feasible LC-MS/MS method was exploited to determine the PK parameters. Form II displayed the most exposure, followed by form I, III, and IV. Notably, all forms showed sex dimorphism, and the bioavailability in the female group was about two-fold higher than in the male group. The PD properties were investigated in carrageenan-induced acute paw inflammation, and form II at 20 mg/kg showed significant inhibition of edema by 42.7%. This study clarified the polymorphic, PK, and PD characters of four crystal forms of CK, and the data suggested that form II had the best efficacy for drug development.
The electronic and optical properties of the defect chalcopyrite XGa2S4 (X=Zn, Cd, Hg) compounds are studied based on the first-principle calculations. Its structural properties are consistent with the earlier experimental and theoretical results, and its electronic and optical properties are discussed in detail in this paper. The results indicate that the three compounds described hare exhibit an anisotropic behaviour in the intermediate energy range (4 eV10 eV), and an isotropic behaviour in the low(4 eV) or high(10 eV) energy range. The refractive index curves of ZnGa2S4 and HgGa2S4 have an inflection point at the plasma frequency p, and their reflectivity reaches a maximal value at p and then declines sharply. Moreover, the calculated optical properties indicate that these compounds can serve as shielding and detecting devices for ultraviolet radiation.
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