Phase drift cancellation of remote radio frequency transfer using an optoelectronic delay-locked loop

In this Letter, we propose a phase drift cancellation method for remote radio frequency transfer. Phase fluctuation along the transmission fiber, which is induced by temperature and pressure changes, is measured and compensated by a heterodyne optoelectronic delay-locked loop. The control loop consists of a heterodyne optoelectronic phase detector, a microwave delay module, and the loop filter. We demonstrate the concept by transmitting a 10?GHz microwave frequency over 50?km single-mode fiber, with subpicosecond jitters measured at the remote end.     

Acoustic scattering from fluid-filled finite cylindrical shell in water:Ⅱ.Experiment

Acoustic scattering from the submerged fluid-filled finite cylindrical shell insonified by an incident plane wave is studied experimentally and theoretically.A monostic broadband transducer with the sharp directivity is used in the experiment.The broadband LFM signal and the single-frequency narrow pulse are used to measure the backscattering field of the cylindrical shell.The measured results have a good agreement with the theory both in time and frequency domain.The theoretical and experimental results show that the resonances of several additional waves which are caused by the internal fluid are presented in the frequency domain.And a series of ’whispering gallery’ waves produced by the waves reflected back and forth in the internal fluid filled in the cylindrical shell are added.The reason for the clustering of the bowl-shape resonance curves in the frequency-angle spectrum is explained as the superposition of the first several modes of ’whispering gallery’ waves.     

离子液体预处理生物质提高糖化产率

采用酶解糖化法检测离子液体EmimAc和AmimCl对生物质(甘蔗渣和桉木)的预处理效果,考察了温度、时间和固/液质量比对离子液体预处理效果的影响。 结果表明, 2种离子液体对2种生物质的最佳预处理温度均为140 ℃,固液质量比均为1∶15,EmimAc对桉木和甘蔗渣的预处理时间分别是12和4 h,而AmimCl所需的时间分别是14和8 h,EmimAc对桉木和甘蔗渣的预处理效果分别是传统方法的13.931和3.886倍,而AmimCl对这2种生物质分别是传统方法的4.665和2.835倍。 可见EmimAc的预处理效果优于AmimCl。     

Highly Efficient Au/TiO2 Catalyst for One‐pot Conversion of Nitrobenzene to p‐Aminophenol in Water Media

Au/TiO₂ catalyst is firstly reported to be efficient in the hydrogenation of nitrobenzene to produce p‐aminophenol with a high PAP selectivity of 81% and overall yield more than 63%. The catalyst is also quite stable and can be reused for at least 4 times with only slight decrease in activity.     

Efficient conversion of primary and secondary alcohols to primary amines

A convenient single-vessel conversion of primary and secondary alcohols to primary amines is reported. Use of this method results in substantially cleaner crude products than similar procedures reported in the literature. A simple work-up also makes this procedure ideal for parallel synthesis.     

Synthesis of differently sized silver nanoparticles on a screen-printed electrode sensitized with a nanocomposites consisting of reduced graphene oxide and cerium(IV) oxide for nonenzymatic sensing of hydrogen peroxide

The authors describe a screen-printed and disposable electrode for the nonenzymatic determination of hydrogen peroxide (H₂O₂). It is based on the controllable synthesis and deposition of silver nanoparticles (AgNPs) of different sizes on a nanocomposite consisting of reduced graphene oxide and cerium (IV) oxide (rGO@CeO₂) that was placed on a screen-printed electrode (SPE). X-ray powder diffractometry and Fourier transform infrared spectroscopy were used to characterize the composition of the hybrid nanomaterials. Electrochemical impedance spectroscopy and scanning electron microscopy were employed to study the interfacial properties and morphologies of different electrodes. The sensor was investigated by cyclic voltammetry and chronoamperometry (i-t plots). After optimization, the modified SPE showed a good performance towards the electrocatalytic reduction of H₂O₂, best at a working potential of ?0.3 V (vs. Ag/AgCl). Features of merit include a broad linear analytical range extending from 0.5 μM to 12 mM, and a limit of detection as low as 0.21 μM (at an S/N ratio of 3). The sensor is simple, quick, stable and reliable. It was applied to the determination of H₂O₂ in (spiked) contact lens care solutions with good accuracy and recovery.

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Graphical abstract An enhanced sensing platform for nonenzymatic hydrogen peroxide (H₂O₂) based on controllable synthesis of differently sized silver nanoparticles (AgNPs) loaded on reduced graphene oxide and cerium(IV) oxide (rGO@CeO₂) nanocomposites to sensitize screen-printed electrode (SPE) was fabricated.

     

A new polyoxometalate-based 3d-4f heterometallic aggregate: a model for the design and synthesis of new heterometallic clusters

A new polytungstoarsenate-based 3d-4f heterometallic aggregate has been synthesized, consisting of three {alpha-AsW10 O 38} fragments bridged by three {Fe-(mu3-O)3-Ce} heterometallic clusters.     

Photocrosslinked methacrylated chitosan-based nanofibrous scaffolds as potential skin substitute

Nanofibers based on natural polymers have recently been attracting research interest as promising materials for use as skin substitutes. Here, we prepared photocrosslinked nanofibrous scaffolds based on methacrylated chitosan (MACS) by photocrosslinking electrospun methacrylated chitosan/poly (vinyl alcohol) (PVA) mats and subsequently removing PVA from the nanofibers. We comprehensively investigated the solution properties of MACS/PVA precursors, the intermolecular action between MACS and PVA components, and the morphology of MACS/PVA nanofibers. Results indicated that the fiber diameter and morphology of the photocrosslinked methacrylated chitosan-based nanofibrous scaffolds were controlled by the MACS/PVA mass ratio and showed highly micro-porous structures with many fibrils. In vitro cytotoxicity evaluation and cell culture experiments confirmed that MACS-based mats with micro-pore structure were biocompatible with L929 cells and facilitated cellular migration into the 3D matrix, demonstrating their potential application as skin replacements for wound repair.     

平顶高斯光束在梯度折射率介质中的传输特性

 利用广义惠更斯-菲涅耳衍射积分法,推导出平顶高斯光束在梯度折射率介质中传输时的解析表达式,对平顶高斯光束在梯度折射率介质中的传输特性进行了分析,讨论了介质梯度折射率系数和光束阶数对传输特性的影响。研究表明,平顶高斯光束在梯度折射率介质中传输时轴上光强分布呈现周期性变化,其周期决定于介质梯度折射率系数,而与光束的阶数无关;轴上峰值处的横向光强分布受梯度折射率系数和光束阶数的影响较大,横向光强的最大值随着梯度折射率系数的增大而增大。