Stability switches, bifurcation, and multi-stability of coupled networks with time delays

This paper reveals the dynamical behaviors of a network consisting of a pair of ring sub-networks and two-way couplings of neurons between the individual sub-networks. Time delays are introduced into the internal connections within the individual sub-networks and the couplings between the individual sub-networks. The stability and instability of the trivial equilibrium of the network are analyzed and the conditions for the existence of Hopf bifurcation are obtained by discussing the associated characteristic equation. The criterion for the global stability of the trivial equilibrium of the network is given by constructing a suitable Lyapunov functional. Numerical simulations are performed to validate the theoretical results and rich dynamical behaviors are observed, such as multiple stability switches of the network equilibrium, synchronous/asynchronous oscillations, and multi-stability.     

Efficient above-band-gap light emission in germanium Invited Paper

We report an above-band-gap radiative transition in the photoluminescence spectra of single crystalline Ge in the temperature range of 20-296 K. The temperature-independence of the peak position at ～0.74 eV is remarkably different from the behavior of direct and indirect gap transitions in Ge. This transition is observed in n-type, p-type, and intrinsic single crystal Ge alike, and its intensity decreases with the increase of temperature with a small activation energy of 56 meV. Some aspects of the transition are analogous to Ⅲ-Ⅴ semiconductors with dilute nitrogen doping, which suggests that the origin could be related to an isoelectronic defect.     

基于介孔碳的电化学酪氨酸酶生物传感器法测定水体中的苯酚及高效液相色谱法评价

采用新型的介孔碳材料作为固载酪氨酸酶的检测平台构建生物传感器,应用于水体环境中苯酚污染物的检测,并通过高效液相色谱法对电化学酪氨酸酶生物传感器法的准确性进行了评价。研究表明,介孔碳的"空间限制效应"能够防止酪氨酸酶(三维尺寸为6.5 nm×9.8 nm×5.5 nm)体外去折叠失活。基于介孔碳材料构建的电化学酪氨酸酶生物传感器在苯酚污染物检测方面显示了优良的性能,其重现性、灵敏度、稳定性、选择性以及检出限均比较令人满意。基于介孔碳的电化学酪氨酸酶生物传感器对苯酚污染物的检出限达到20 nmol/L,线性范围为0.1~10 μmol/L。采用基于介孔碳的电化学酪氨酸酶生物传感器和高效液相色谱法对实际水样品进行测定结果比对,结果表明该生物传感器方法检测结果准确、有效,适合于苯酚污染物突发污染事件的应急检测。     

Sagnac型光学电压互感器传感单元非线性误差分析与抑制

基于Pockels效应的Sagnac型光学电压互感器的传感单元是由法拉第准直旋光器和BGO晶体构成,其中由偏振串扰引入的非线性误差是影响互感器测量精度及稳定性的主要误差来源。为了抑制传感单元存在的非线性误差,从主要光路器件及器件间的耦合点中分析产生偏振串扰的非理想耦合点及耦合机理,并提取表征该耦合点的误差特征参量,建立各非理想耦合点的传输模型,由此推导由传感单元偏振串扰引入的非线性误差模型,数值仿真并实验验证非理想偏振耦合对互感器性能的影响。在此基础上,提出了由BGO晶体敏感环境振动、温度波动等产生的非线性误差的抑制方法,实验结果验证了抑制方法的有效性。     

Simultaneous detection of four flavonoids and two alkaloids in rat plasma by LC–MS/MS and its application to a comparative study of the pharmacokinetics between Abri Herba and Abri mollis Herba extract after oral administration

Abri Herba and Abri mollis Herba both were important members of the Leguminosae family in southwestern China. Abri mollis Herba was often used as Abri Herba due to their proximity, but there are few studies on pharmacokinetics to compare their main identical active compositions. A sensitive and selective high‐performance liquid chromatography with tandem mass spectrometry method in the positive/negative electrospray ionization switching mode was developed and validated for the simultaneous analysis of four flavonoids and two alkaloids in rat plasma. The chromatographic separation was carried out on a C18 column with a gradient mobile phase consisting of methanol and 0.5% acetic acid. The detection of the target compounds was conducted in multiple‐reaction monitoring mode with a hybrid triple quadrupole linear ion trap mass spectrometer equipped with positive/negative ion‐switching electrospray ion source. The differences in pharmacokinetics were discovered, which indicated that the substitution between them is some degree of irrationality. The validated method was successfully applied to pharmacokinetic study of the six components in male rat plasma after oral administration of Abri Herba and Abri mollis Herba extract and the results in the study would provide a useful guide for the clinical application of Abri Herba with those in Abri mollis Herba.     

一种新型金属铱(Ⅲ)有机配合物的光谱特性研究

针对一种合成的新型金属铱(Ⅲ)有机配合物的光谱特性进行了研究.实验中,该配合物的配体为苯基喹啉和异丁基酰苯胺.紫外-可见吸收光谱研究表明,该配合物分别在225 nm,267 nm、339 nm以及460 nm附近出现较强吸收峰,其中在320 nm～580 nm范围内,存在着单线态和三线态的金属铱到配体的电荷跃迁.发光光谱测试表明,随着溶液中(二氯甲烷作为溶剂)该新型金属铱(Ⅲ)有机配合物浓度的增加.溶液的发光光谱峰值位置不断发生红移.当处在460 nm激发波长下,溶剂二氯甲烷发光光谱没有出现明显的峰值强度,排除了溶剂对发光光谱测量的影响,直接测量出该配合物在606 nm附近有强的金属二线态磷光发射.因此,该配合物有望成为一种可用于有机电致发光领域的新型磷光材料.     

Effects of Ce on the spectroscopic properties of transparent phosphate glass ceramics co-doped with Er/Yb

We have prepared Er³⁺/Yb³⁺ co-doped transparent phosphate glass ceramics by the high-temperature melting technique, and demonstrated the influence of energy acceptors Ce³⁺ ions on the up-conversion and 1.54 μm emission properties of Er³⁺. The energy transfer mechanism is discussed based on the energy matching and the energy level structure. The phonon-assisted energy transfer between Er³⁺ and Ce³⁺ favors population feeding from the ⁴I_11/2 to the ⁴I_13/2 level, and therefore drastically decreases the up-conversion emission intensity of Er³⁺. Meanwhile, 1.54 μm fluorescence enhances greatly with the introduction of Ce³⁺ ions at the proper concentration.     

AEROELASTIC OPTIMIZATION DESIGN OF COMPOSITE WING WITH CONSIDERATION OF STRUCTURAL INSTABILITY

从工程数学求解和有限元分析角度对复合材料结构的稳定性分析方法进行研究,基于这两个方面分别建立了同时考虑壁板稳定性约束和气动弹性约 束的气动弹性优化技术,并以大展弦比复合材料机翼为对象,进行气动弹性综合优化设计。研究表明,机翼气动弹性优化中若不考虑稳定性约束条件,虽然可以获得较小结构重量,但往往不满足稳定性要求;相比从有限元角度考虑结构失稳特征的气动弹性综合优化设计方法,通过工程数学方法对机翼结构进行分区失稳分析优化可以更加精准地控制变量,在满足各项性能指标,特别是稳定性约束的同时,进一步减轻了结构重量,提高了结构失稳因子。     

Near-infrared Aza-BODIPY Dyes Through Molecular Surgery for Enhanced Photothermal and Photodynamic Antibacterial Therapy

The widespread use of high-dose antibiotics will not only lead to the rapid acquisition of antibiotic resistance and increased incidence of drug-resistant bacterial infections, but also produce toxic side effects on normal tissues. Herein, two near-infrared dyes BDP-4PTZ and BDP-4DPA were synthesized, and the electron donors of diphenylamine and phenothiazine with the only difference of sulphur(S)-lock between the two phenyl rings were introduced onto the electron acceptor aza-dipyrromethene boron difluoride(aza-BODIPY) through molecular surgery. Through co-precipitation into nanoparticles(NPs), BDP-4PTZ NPs and BDP-4DPA NPs were fabricated with good biocompatibility. Upon 660 nm photoirradiation, BDP-4PTZ NPs and BDP-4DPA NPs showed excellent photothermal conversion efficiency(43% and 50%, respectively) and reactive oxygen species(ROS) production performance(ca. 3.6 and 6 times higher than that of indocyanine green, respectively). In vitro antibacterial experiments indicated that both NPs could effectively destroy the bacteria's membrane to eradicate drug-resistant bacteria. Furthermore, the bacterial abscess was effectively eliminated after treatment with BDP-4DPA NPs under 660 nm photoirradiation without adverse effects. Thus, through molecular surgery, BDP-4DPA without the S-lock demonstrates synergistic photothermal and photodynamic antimicrobial activities, which is promising for further molecular design towards effective neo-antimicrobial phototherapy.