The optical properties of Tm3+ doped Na5Lu9F32 single crystal

Tm3+ doped Na5Lu9F32 single crystal with high optical quality was grown by an improved Bridgman method. The Judd-Ofelt intensity parameters Ωt (t=2, 4, 6) were calculated according to the measured absorption spectra and physical-chemical properties of the obtained Na5Lu9F32 single crystal. The stimulated emission cross-section of the 3F4→3H6 transition (~1.8 μm) is 0.35×10-20 cm2 for Tm3+ doped Na5Lu9F32 single crystal. The emission spectra under the excitation of 790 nm laser diode (LD) and fluorescence lifetime at 1.8 μm were measured to reveal the fluorescence properties of Tm3+ doped Na5Lu9F32 single crystal. The research results show that the Tm3+ doped Na5Lu9F32 single crystal has larger stimulated emission cross-section compared with other crystals. All these spectral properties suggest that this kind of Tm3+doped Na5Lu9F32 crystal with high physical-chemical stability and high-efficiency emission at 1.8 μm may be used as potential laser materials for optical devices.     

A statistically harmonized alignment-classification in image space enables accurate and robust alignment of noisy images in single particle analysis

In determining the three-dimensional (3D) structure of macromolecular assemblies in single particle analysis, a large representative dataset of two-dimensional (2D) average images from huge number of raw images is a key for high resolution. Because alignments prior to averaging are computationally intensive, currently available multireference alignment (MRA) software does not survey every possible alignment. This leads to misaligned images, creating blurred averages and reducing the quality of the final 3D reconstruction. We present a new method, in which multireference alignment is harmonized with classification (multireference multiple alignment: MRMA). This method enables a statistical comparison of multiple alignment peaks, reflecting the similarities between each raw image and a set of reference images. Among the selected alignment candidates for each raw image, misaligned images are statistically excluded, based on the principle that aligned raw images of similar projections have a dense distribution around the correctly aligned coordinates in image space. This newly developed method was examined for accuracy and speed using model image sets with various signal-to-noise ratios, and with electron microscope images of the Transient Receptor Potential C3 and the sodium channel. In every data set, the newly developed method outperformed conventional methods in robustness against noise and in speed, creating 2D average images of higher quality. This statistically harmonized alignment-classification combination should greatly improve the quality of single particle analysis.     

担载Na、W、Mn的(001)SiO2单晶模型催化剂的SEM研究一多组分Na、W、Mn的分布形态及其在SiO2基体中的扩散行为

用浸渍法制备了担载多组分Na、W、Mn的(001)SiO2单晶模型催化剂,并进行了XPS和SEM表征。研究结果表明,Na、W、Mn的多元组合使SiO2转变为SiO32-能力的大小顺序依次为WMn>NaWMn>NaMn>NaW,它们在SiO2表面的形态各不相同,并且在SiO2基体中的扩散程度比单组分强,表明它们之间可能存在着某种相互促进向SiO2基体中扩散的协同效应。