Two series of unconventional triazine‐based dendrimers with C2 symmetry and C3 symmetry were prepared. The newly prepared C3‐symmetrical dendrimers were characterized by 1H and 13C NMR spectroscopy, mass spectrometry, and elemental analysis. Differential scanning calorimetry, polarizing microscopy, and powder XRD showed that the C3‐symmetrical dendrimers display columnar liquid‐crystalline phases during thermal treatment, but the C2‐symmetrical dendrimers were not observed to behave correspondingly. The molecular conformations of C3‐ and C2‐symmetrical dendrimers were obtained by computer simulation with the MM2 model of the CaChe program in the gas phase. The simulation results reasonably explain the different mesogenicities of C3‐ and C2‐symmetric dendrimers. This new strategy should be applicable to other types of unconventional dendrimers with rigid frameworks for displaying columnar liquid‐crystalline behavior. 相似文献
2-μm lasers with high pulse energy and long pulse width of hundreds of nanoseconds are needed urgently in the accurate wind
velocity lidar systems. This paper presents the acoustic-optical Q-switched Tm:YAG laser performance in a pulsed-laser-diode
end-pumping figure-eight ring resonator structure. Pulse energy and pulse width are investigated with the increasing of the
incident pump energy at different repetition rate operation. Maximum energy of 4.6 mJ with the pulse width of 179.2 ns and
3.57 mJ with pulse width of 184.4 ns are obtained at the repetition rate of 20 and 100 Hz, respectively. Under free-running
and Q-switched operation, the peak output wavelength is 2.014 μm at all time, and the beam quality factors are lower than
2 times diffraction-limited measured by a knife-edge traveling method. 相似文献
Live cell imaging of protein-specific glycoforms is important for the elucidation of glycosylation mechanisms and identification of disease states. The currently used metabolic oligosaccharide engineering (MOE) technology permits routinely global chemical remodeling (GCM) for carbohydrate site of interest, but can exert unnecessary whole-cell scale perturbation and generate unpredictable metabolic efficiency issue. A localized chemical remodeling (LCM) strategy for efficient and reliable access to protein-specific glycoform information is reported. The proof-of-concept protocol developed for MUC1-specific terminal galactose/N-acetylgalactosamine (Gal/GalNAc) combines affinity binding, off-on switchable catalytic activity, and proximity catalysis to create a reactive handle for bioorthogonal labeling and imaging. Noteworthy assay features associated with LCM as compared with MOE include minimum target cell perturbation, short reaction timeframe, effectiveness as a molecular ruler, and quantitative analysis capability. 相似文献
Hybrid perovskites have generated a great deal of interest because of their potential in photovoltaic applications. However, the toxicity of lead means that there is interest in finding a nontoxic substitute. Bulk single crystals of both cubic CH3NH3SnI3 and CH(NH2)2SnI3 were obtained by using the top‐seeded solution growth method under an ambient atmosphere. Structural refinement, band gap, thermal properties, and XPS measurements of CH3NH3SnI3 and CH(NH2)2SnI3 single crystals are also reported in detail. These results should pave the way for further applications of CH3NH3SnI3 and CH(NH2)2SnI3. 相似文献
A novel Pd(II)-dibenzo-18-crown-6 (DB18C6) complex [K(DB18C6)]2[Pd(SCN)4] has been isolated and characterized by X-ray diffraction analysis. In the solid state, it displays a quasi-one-dimensional infinite chain of two [K(DB18C6)] + complex cations and a [Pd(SCN)4]2- anion bridged by K+-p interactions between adjacent [K(DB18C6)] + units. 相似文献
An adaptive fast multipole higher order boundary element method combining fast multipole (FM) with a higher order boundary element method is studied to solve the power frequency electric field (PFEF) of substations. In this new technique, the iterative equation solver GMRES is used in the FM, where matrix-vector multiplications are calculated using fast multipole expansions. The coefficients in the preconditioner for GMRES are stored and are used repeatedly in the direct evaluations of the near-field contributions. Then a 500kV outdoor substation is modeled and the PFEF of the substation is analyzed by the novel algorithm and other conventional methods. The results show that, in computational cost and the storages capability aspects, the algorithm proposed in this study has obvious advantages. It is suitable for the calculation of the large-scale PFEF in complex substations and the design of electromagnetic compatibility. 相似文献
Short resonant cavity which owns broad free spectral range is useful to select single-frequency. We take Tm,Ho:YLF (Tm 6%;
Ho 0.4%) microchip pumped by diode laser to attain high efficiency single-longitudinal-mode laser. Both end faces are coated.
The microchip is the oscillate cavity itself. It’s placed in the Dewar flask, which is filled with liquid nitrogen to keep
the temperature at 77 K. Comparison of the laser characteristics between a 0.9 mm microchip and a 0.5 mm microchip were expressed
in this report. The maximum single-longitudinal-mode power are 33 and 76 mW, corresponding the slope efficiency of both lasers
are 12 and 37%, separately. The beam quality is about 1.06 and 6.8 for 0.9 mm microchip and 0.5 mm microchip, measured by
the knife-edge method. 相似文献
The accuracy of spectrograms may be affected by baseline excursion or drift when infrared spectrometers are used in the analyses of gases. Background deduction or baseline correction is one of the effective pretreatment methods that can improve measurement accuracy. This paper presents a novel methodology based on complex wavelet transform algorithm to perform background deduction. The complex wavelet transform methodology establishes a complex wavelet filter to decompose the spectral signals first, and set the decomposition coefficients in the high-frequency section to zero, and then reconstruct the background signals; finally, the background deduction can be realized by deducting the background signals. In this study, the complex wavelet established by Daubechies was selected to demonstrate background deduction aiming at simulative spectral signals with different backgrounds and the real spectral signal of SF6 decomposition gases. Compared with the results done by the real wavelet transform in the same conditions, the results indicate that complex wavelet transform methodology can perform background deduction more efficiently than real wavelet transform methodology, thus improving the effectiveness and precision of spectrogram measurements greatly, which is useful for SF6 gas decomposition compositions analysis