The role of hydrogen bonding on a hydroxylated liquid crystal, bis [4-(5-hydroxypentyloxycarbonyl)phenylene] terephthalate

Hydroxyl-terminated liquid crystalline bis[4-(5-hydroxypentyloxycarbonyl)phenylene] terephthalate (BHT) was prepared and compared with its non-hydroxylated analog, bis[4-(pentyloxycarbonyl)phenylene] terephthalate (BPT). BHT, with the possibility to form intermolecular hydrogen bonding (H-bonding), has higher thermal transition temperatures (T_m and T_i) than BPT. Infrared spectroscopy was applied to prove the existence of H-bonding for BHT. An X-ray diffraction study suggests that the smectic A (S_A) phase is the only phase existing for BPT but for BHT, an interdigitated layered structure was found to be mixed with the S_A phase. The formation of this interdigitated layered structure is mainly due to the intermolecular H-bonding between the terminal hydroxyl and the external ester groups in BHT.     

裂变产物中短寿命核素138Cs的分离提取

本文研究了从裂变产物中分离提取短寿命核素138Cs的方法.通过两步沉淀和一步溶剂萃取,实现138Cs与其他裂片核素的分离.γ能谱分析表明,138Cs对其他裂片核素的去污系数＞103,138Cs的化学回收率为45.0%.     

二次偏振调制测距系统中调制频率与测距精度的关系

本文在基于二次偏振调制激光测距系统的基础上, 对调制频率与激光测距系统精度的关系做了深入的理论推导和实验验证. 最终得出结论: 相位法激光测距系统的测量精度会随着调制频率的增大而提高, 且精度的提高程度正比于调制频率的不确定度Δf与测程范围内半波长数N值的比值. 并通过选取合适的调制频率来提高系统的测距精度, 提高后的测距精度可达10^-7.     

探索萤火鱿发光的微观机理,揭示生物发光的奥秘

<正>在科幻电影《阿凡达》中,潘多拉星球上美轮美奂的发光生物给观众留下了深刻的印象。导演卡梅隆的想象力无疑来自于地球上的生物发光(bioluminescence)现象。无论是诗句"银烛秋光冷画屏,轻罗小扇扑流萤",还是世界各地的荧光海滩,都是普通大众所感受到的生物发光现象。生物发光是活体生物通过化学反应产生可见光的现象,是一种特殊类型的化学发光。目前已发现多达17个门中700多个属的生物物种具有发     

反相高效液相色谱法测定水中的甲基磺草酮农药

建立了二氯甲烷萃取浓缩,反相高效液相色谱测定水样中甲基磺草酮农药含量的分析方法.调节水样pH值为4.0后,以二氯甲烷为萃取剂,25℃下重复萃取两次,萃取时间为15min,旋转蒸发仪浓缩近干,乙腈定容.以SPHERI-5RP-18 （5μm）为色谱柱,乙腈-磷酸缓冲溶液（pH值4.0）为流动相,紫外检测波长为220nm.结果表明,在选定的萃取和色谱条件下,甲基磺草酮测定的线性范围为0.5-100.0mg/L,线性相关系数r为0.9996,标准偏差（SD）为0.46,变异系数（CV）为0.47％,平均加标回收率88.9％,检出限为0.03mg/L.此方法可用于实际水样中甲基磺草酮农药含量的测定.     

基于光参量放大的高速实时光取样技术

提出了一种基于光参量放大的高速实时光取样方案. 利用色散介质对光纤锁模激光器产生的窄脉冲源进行色散展宽,从而产生线性啁啾光信号. 将该信号和被取样信号同时送入高非线性光纤,利用高非线性光纤中的参量放大效应,将被取样信号的强度信息调制到线性啁啾光信号上. 在接收端利用不同中心波长的滤波器即可滤出不同时间点的取样信号,从而在光域同时完成了高速实时光取样和取样信号的串-并转换. 是实现高速实时取样技术的一种极具竞争力的实现方案. 实验中,实现了对10 Gb/s非归零码OOK信号的40 GS/s的高速实时取样系统,并转换为4路10 GS/s取样信号输出. 在接收端成功根据4路取样信号恢复出被取样信号波形,验证了该实时光取样方案的可行性. 关键词： 光信号处理 光取样 参量放大 高非线性光纤     

Ionic strength and pH reversible response of visible and near-infrared fluorescence of graphene oxide nanosheets for monitoring the extracellular pH

The visible and near-infrared (vis-NIR) fluorescence of graphene oxide nanosheets (GO) shows a reversible and sensitive response to ionic strength and pH, in particular a linear physiological pH dependence for monitoring extracellular pH evolution during growth and metabolism of normal and cancer cells.     

N-丁基-3,6-二乙酰基咔唑的合成及表征

以咔唑为合成原料,在相转移催化剂作用下合成N-丁基咔唑,作为电子给体和共轭桥中心,乙酰氯作为端基电子受体,合成了V型化合物:N-丁基3,6-二乙酰基咔唑。其结构经IR,1H NMR和GC-MS表征。     

Investigation of the guided-mode characteristics of hollow-core photonic band-gap fibre with interstitial holes

This paper investigates the guided-mode characteristics of hollow-core photonic band-gap fibre (HC-PBGF) with interstitial holes fabricated by an improved twice stack-and-draw technique at visible wavelengths. Based on the simulation model with interstitial holes, the influence of glass interstitial apexes on photonic band-gaps is discussed. The existing forms of guided-mode in part band gaps are shown by using the full-vector plane-wave method. In the experiment, the observed transmission spectrum corresponds to the part band gaps obtained by simulation. The fundamental and second-order guided-modes with mixture of yellow and green light are observed through choosing appropriate fibre length and adjusting coupling device. The loss mechanism of guided-modes in HC-PBGF is also discussed.     

Investigation of gain recovery for InAs/GaAs quantum dot semiconductor optical amplifiers by rate equation simulation

The gain recoveries in quantum dot semiconductor optical amplifiers (QD SOAs) are numerically studied by rate equation simulation. Similar to the optical pump-probe experiment, the injection of double 150 fs optical pulses is used to simulate the gain recovery of a weak continuous signal under different injection levels, inhomogeneous broadenings, detuning wavelengths, and pulse signal energies for the QD SOAs. The obtained gain recoveries are then fitted by a response function with multiple exponential terms to determine the response times. The gain recovery can be described by three exponential terms with the time constants, which can be explained as carrier relaxation from the excited state to the ground state, carrier captured by the excited state from the wetting layer, and the supply of the wetting layer carriers. The fitted lifetimes decrease with the increase of the injection currents under gain unsaturation, slightly decrease with the decrease of inhomogeneous broadening of QDs, and increase with the increase of detuning wavelength between continuous signal and pulse signal and the increase of the pulse energy.