Achieving room temperature phosphorescence from organic small molecules on amino acid skeleton

Room temperature phosphorescence (RTP) generated by small molecules has attracted great attention due to their unique potentials for biosensor, bioimaging and security protection. While, the design of RTP materials is extremely challenging for organic small molecules in non-crystalline solid state. Herein, we report a new strategy for achieving non-crystalline organic small molecules with RTP emission by modifying different phosphors onto diphenylalanine or phenylalanine derivatives. Benefiting from the skeletal structure of the amino acid derivatives, there are intermolecular hydrogen bond formation and rigidification effect, thereby minimizing the intermolecular motions and enhancing their RTP performance     

Hybrid EuIII Coordination Luminophore Standing on Two Legs on Silica Nanoparticles for Enhanced Luminescence

In this study, we have demonstrated a two-legged, upright molecular design method for monochromatic and bright red luminescent Ln^III-silica nanomaterials. A novel Eu^III-silica hybrid nanoparticle was developed by using a doubly binding TPPO−Si(OEt)₃ (TPPO: triphenyl phosphine oxide) linker. The TPPO−Si(OEt)₃ was confirmed by ¹H, ³¹P, ²⁹Si NMR spectroscopy and single-crystal X-ray analysis. Luminescent Eu(hfa)₃ and Eu(tfc)₃ moieties (hfa: hexafluoroacetylacetonate, tfc: 3-(trifluoromethylhydroxymethylene)camphorate) were fixed onto TPPO−Si(OEt)₃-modified silica nanoparticles, producing Eu(hfa)₃(TPPO−Si)₂-SiO₂ and Eu(tfc)₃(TPPO−Si)₂-SiO₂, respectively. Eu(hfa)₃(TPPO−Si)₂−SiO₂ exhibited the higher intrinsic luminescence quantum yield (93 %) and longer emission lifetime (0.98 ms), which is much larger than those of previously reported Eu^III-based hybrid materials. Eu(tfc)₃(TPPO−Si)₂−SiO₂ showed an extra-large intrinsic emission quantum yield (54 %), although the emission quantum yield for the precursor Eu(tfc)₃(TPPO−Si(OEt)₃)₂ was found to be 39 %. These results confirmed that the TPPO−Si(OEt)₃ linker is a promising candidate for development of Eu^III-based luminescent materials.     

速调型相对论返波管理论研究

对速调型相对论返波管慢波结构色散特性及束波相互作用进行了理论研究。色散特性研究表明：器件工作模式为TM01模,近点,耦合阻抗较高。色散特性预测的工作频率与粒子模拟结果非常接近。慢波结构峰值增长率相对较小,这与电子束与慢波结构相距较大有关,因而器件从起振到饱和的时间较长。在束波相互作用理论中,全面考虑了电子束与慢波结构前向波基波、反向波－1次空间谐波及空间电荷场相互作用、谐振反射器对电子束进行的束流调制和能量调制作用,以及调制腔和提取腔处引入的耦合阻抗及轴向波数突变。稳态和非稳态计算结果均获得了超过40%的束波转换效率。     

Performance improvement of electrochromic display devices employing micro-size precipitates of tungsten oxide

In this paper, we studied the effect of micro-size WO₃ precipitates on the electrochromic characteristics based on aging test. The electrochromic mechanism can be effectively investigated by a solid-state TaN/WO₃/ITO capacitor. The experimental results reveal that WO₃ electrochromic devices with optimized aging time of 4 days exhibit a higher optical contrast and longer retention time, which is mainly attributed to the formation of micro-size WO₃ precipitates during aging process. The performance improvement using micro-size WO₃ precipitates has the potential in future large-area window or energy efficient display applications.     

DNA Degradation of Genetically Modified Cottonseed Meal During Feed Processing

The effects of dry heating, wet heating, and extrusion on the degradation of DNA in cottonseed meal (CSM) were studied using polymerase chain reaction (PCR) and real-time PCR approach. Both the sad1 DNA, ranging between 128 and 883 bp in size, and the cry1Ab/c gene, ranging between 183 and 652 bp in size, were detectable in all dry-heated CSM and cottonseed. During wet heating, the sad1 gene (≥883 bp) and the cry1Ab/c (≥952 bp) gene were thoroughly degraded at 105 and 120 °C, respectively. Sizes from 128 to 530 bp for the sad1 gene and sizes from 183 to 652 bp for the cry1Ab/c gene were detected during extrusion at temperatures ranging from 75 to 135 °C. Fragments ≤883 bp for the sad1 gene and ≤952 bp for the cry1Ab/c gene were detected in all of the extruded samples with water content varying between 26 and 34 %. The copy number ratio of cry1Ab/c to sad1 in samples of Bt cottonseed meal decreased rapidly when the temperature increased during the heating process. In conclusion, feed processing markedly degrades the larger DNA fragments of sad1 and cry1Ab/c, with high temperature and water content being the main factors for that degradation.     

Alternating copolymers of hexafluoroisobutylene with vinyl trifluoroacetate and vinyl pentafluorobenzoate

Copolymerizations of hexafluoroisobutylene (HFIB) with vinyl pentafluorobenzoate (VPFB) and vinyl trifluoroacetate (VTFA) were carried out in bulk using perfluorodibenzoyl peroxide as the radical initiator. The copolymers obtained were characterized by proton and fluorine NMR spectroscopy. The monomer reactivity ratios in the polymerization of HFIB with VPFB were r₁ (HFIB) = 0, r₂ (VPFB) = 0.373, and r₁r₂ = 0. The results indicated that these copolymers have alternating structures. Similarly, the copolymers of HFIB and VTFA also showed alternating structures. The films of HFIB‐co‐VPFB were prepared by casting THF solution of polymers. Films obtained were flexible and transparent. The refractive indices of copolymers were 1.4549, 1.4490, and 1.4438 at 532, 633, and 839 nm, respectively. The average T_gs of HFIB‐co‐VTFA and HFIB‐co‐VPFB were 52 and 71 °C, respectively. From these results, the T_g of the hypothetical HFIB homopolymer is postulated to be in between 70 and 90 °C, which may be useful in the assessment of T_gs of HFIB copolymers with other vinyl monomers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Physical,hydrochemical and isotopic characteristics of springs in Beijing,China, compared to historical properties

A physical, hydrochemical and isotopic evaluation of springs in Beijing was conducted in 2009 to reveal apparent changes in the properties of those springs. The results showed that most of the 2nd class springs and more than 50 % of the 1st class springs recorded in the early 1980s were depleted, while the discharges of existing springs have also decreased sharply. In addition, the majority of springs were of the HCO₃–Ca–Mg type and good water quality, with the quality indices changing slightly compared to those recorded 30 years ago. The abundances of ²H, ¹⁸O, and ³H in the springs indicated that most of the springs were of meteoric origin with a relatively close connection to modern atmospheric precipitation. As a result, the springs have a relatively strong renewability within a shallow circulation.     

Complex dynamic behavior in a viral model with state feedback control strategies

With the consideration of mechanism of prevention and control for the spread of viral diseases, in this paper, we propose two novel virus dynamics models where state feedback control strategies are introduced. The first model incorporates the density of infected cells (or free virus) as control threshold value; we analytically show the existence and orbit stability of positive periodic solution. Theoretical results imply that the density of infected cells (or free virus) can be controlled within an adequate level. The other model determines the control strategies by monitoring the density of uninfected cells when it reaches a risk threshold value. We analytically prove the existence and orbit stability of semi-trivial periodic solution, which show that the viral disease dies out. Numerical simulations are carried out to illustrate the main results.     

Synthesis,structural characterization and catalytic activity of benzimidazole‐functionalized Pd(II) N‐heterocyclic carbene complexes

Two Pd(II)–NHC complexes bearing benzimidazole and pyridine groups have been successfully prepared and fully characterized by NMR and X‐ray diffraction analysis. The structure of palladium complexes are a typical square‐planar with palladium surrounded by two pairs of trans‐arranged benzimidazole and carbene ligands. The Pd–NHC complexes have been proved to be a highly efficient catalyst for the Mizoroki–Heck coupling reaction of aryl halides with various substituted acrylates under mild conditions in excellent yields. Copyright © 2013 John Wiley & Sons, Ltd.     

Simulation and feature analysis for gas emboli Doppler ultrasound signals

The purpose of this study is to establish the simulation model of the gas emboli by analyzing reasons for features of gas emboli Doppler ultrasound signals.It is useful for the further classification of the solid emboli and gas emboli.First,the model of the radiation force and the drag force is used to calculate forces acting on the gas emboli.Second,the acceleration of the gas emboli is calculated in both the radial direction and the axial direction of the vessel, which is used to calculate the trajectory of the gas emboli in the vessel.Finally,the computer simulation model is established for the gas emboli.Doppler ultrasound signals of the gas emboli and the solid emboli are generated in the simulation experiment.Experimental results show that compared with the solid emboli,the gas emboli acted by the radiation force and the drag force will result in the frequency-domain broaden in the Doppler spectrogram.When the gas emboli circulate from the low speed area to the high speed one and then from the high speed area back to the low speed one,a "V" shape will be shown in the spectrogram of gas emboli signals.When the gas emboli circulate from the low speed area to the high speed one or from the high speed area to the low speed one,a diagonal shape will be shown for gas emboli signals. It is also shown that features of simulated gas emboli signals match with those of gas emboli signals sampled from clinic.All demonstrate that the simulation method of the gas emboli is reasonable.