Birefringent materials are of great
importance in optical communication
and the laser industry, as they can modulate the polarization of light.
Limited by their transparency range, few birefringent materials, except
α-BaB2O4 (α-BBO), can be practically
used in the deep ultraviolet (UV) region. However, α-BBO suffers
from a phase transition and does not have enough transparency in the
deep UV region. By introducing the relatively small alkali metal Na+ cation and the F– anion to keep the favorable
structural features of α-BBO, we report a new birefringent crystal
Na3Ba2(B3O6)2F (NBBF), which has the desirable optical properties. NBBF not only
maintains the large birefringence (Δn = n
o – n
e =
0.2554–0.0750 from 175 nm to 3.35 μm) and extends its
UV cutoff edge to 175 nm (14 nm shorter than α-BBO) but also
eliminates the phase transition and has the lowest growth temperature
(820 °C) among birefringent materials. These results demonstrate
that NBBF is an attractive candidate for the next generation of deep
UV birefringent materials.
A new approach is presented for the measurement of the self-diffusion coefficients of molecules in solution. It has been applied to metabolites in biofluids such as seminal and blood plasma at physiological temperature. The method is based on the double-gradient-spin-echo pulse sequence in which CPMG and bipolar gradient pulses have been implemented. The double-gradient spin-echo is shown to be useful in reducing the thermal convection that can cause over-estimation of the diffusion coefficients. The multiple spin-echoes in association with the CPMG approach is also insensitive to background gradient artifacts. In addition, the CPMG sequence enables longer diffusion periods (up to seconds) to be used without phase distortion; therefore, the proposed method is suitable for determining the diffusion coefficients of small metabolites in biofluids, where the resonances of large molecules, such as proteins, are suppressed during the spin-echo period as a result of their fast relaxation.
A combination of 1 H nuclear magnetic resonance (NMR) spectroscopy and principal component analysis (PCA) has shown the potential for being a useful method for classification of type, production origin or geographic origin of wines. In this preliminary study, twenty-one bottled wines were classified/separated for their location of production in Shacheng, Changli and Yantai, and the types of the blended, medium dry, dry white and dry red wines, using the NMR-PCA method. The wines were produced by three subsidiary companies of an enterprise according to the same national standard. The separation was believed to be mainly due to the fermentation process for different wines and environmental variations, such as local climate, soil, underground water, sunlight and rainfall. The major chemicals associated with the separation were identified.
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