Self-compression of stimulated Raman backscattering by flying focus

A novel regime of self-compression is proposed for plasma-based backward Raman amplification(BRA) upon flying focus. By using a pumping focus moving with a speed equal to the group velocity of stimulated Raman backscattering(SRBS), only a short part of SRBS which does always synchronize with the flying focus can be amplified. Due to the asymmetrical amplification, the pulse can be directly compressed in the linear stage of BRA. Therefore, instead of a short pulse, the Raman spontaneous or a long pulse can seed the BRA amplifiers. The regime is supported by the 2D particle-in-cell(PIC) simulation without a seed, presenting that the pump pulse is compressed from 26ps to 116fs, with an output amplitude comparable with the case of a well-synchronized short seed. This method provides a significant way to simplify the Raman amplifiers and overcome the issue of synchronization jitter between the pump and the seed

Generation of subcycle isolated attosecond pulses by pumping ionizing gating

We present a novel approach named as pumping ionizing gating (PIG) for the generation of isolated attosecond pulses (IAPs). In this regime, a short laser is used to ionize a pre-existing gas grating, creating a fast-extending plasma grating(FEPG) having an ionization front propagating with the velocity of light. A low-intensity long counterpropagating pump pulse is then reflected by a very narrow region of the ionization front, only where the Bragg conditions for resonant reflection is satisfied. Consequently, the pump reflection is confined within a sub-cycle region called PIG, and forms a wide-band coherent IAP in combination with the frequency up-conversion effect due to the plasma gradient. This approach results in a new scheme to generate IAPs fromlong picosecond pump pulses. Three-dimensional (3D) simulations show that a 1.6-ps, 1-{\mu}m pump pulse can be used to generate a 330 as laser pulse with a peak intensity approximately 33 times that of the pump and a conversion efficiency of around 0.1%.These results highlight the potential of the PIG method for generating IAPs with high conversion efficiency and peak intensity.Comment: It provides a new way to generate isolated attosecond pulse(IAP) by a picosecond pump, which has a protential to boost the IAP energy to joule leve

PEO—PPO—PEO嵌段共聚物的聚集行为及其在胶团萃取中的应用

从分子水平研究了PEO-PPO-PEO嵌段共聚物聚集过程中分子基团微环境和构象的变化．FTIR光谱给出了温度、溶剂、嵌段共聚物组成等影响PEO-PPO-PEO嵌段共聚物胶团结构的定量信息．用无机盐和脂肪醇调控PEO-PPO-PEO嵌段共聚物聚集，荧光光谱技术提供了降低PPO链段与水的相互作用，推动嵌段共聚物在水中胶团化的证据．用水凝胶包埋PEO-PPO-PEO嵌段共聚物，实现了萃取水中低浓度多环芳烃的工艺循环

aggregationbehaviorofpeoppopeoblockcopolymersandtheirapplicationinmicellarextraction

从分子水平研究了PEO-PPO-PEO嵌段共聚物聚集过程中分子基团微环境和构象的变化．FTIR光谱给出了温度、溶剂、嵌段共聚物组成等影响PEO-PPO-PEO嵌段共聚物胶团结构的定量信息．用无机盐和脂肪醇调控PEO-PPO-PEO嵌段共聚物聚集，荧光光谱技术提供了降低PPO链段与水的相互作用，推动嵌段共聚物在水中胶团化的证据．用水凝胶包埋PEO-PPO-PEO嵌段共聚物，实现了萃取水中低浓度多环芳烃的工艺循环

PEO—PPO—PEO嵌段共聚物的聚集行为及其在胶团萃取中的应用

从分子水平研究了PEO-PPO-PEO嵌段共聚物聚集过程中分子基团微环境和构象的变化．FTIR光谱给出了温度、溶剂、嵌段共聚物组成等影响PEO-PPO-PEO嵌段共聚物胶团结构的定量信息．用无机盐和脂肪醇调控PEO-PPO-PEO嵌段共聚物聚集，荧光光谱技术提供了降低PPO链段与水的相互作用，推动嵌段共聚物在水中胶团化的证据．用水凝胶包埋PEO-PPO-PEO嵌段共聚物，实现了萃取水中低浓度多环芳烃的工艺循环

Simultaneous Determination of 76 Veterinary Drugs and Their Metabolites in Pork by QuEChERS-Ultra High Performance Liquid Chromatography-Tandem Mass Spectrometry

In order to improve the efficiency of the detection of multiple veterinary drug residues in pork, a method for the simultaneous determination of 5 types of 76 veterinary drugs and their metabolites residues in pork, including quinolones, sulfonamides, nitroimidazoles, macrolides and benzimidazoles, was established by QuEChERS combined with ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The samples were extracted with acidified acetonitrile and salted out by anhydrous sodium sulfate. The extract was divided into two parts after purified by C18 and anhydrous magnesium sulfate. One part was used for direct determination of the 22 weakly polar compounds, and the other part was concentrated by nitrogen blowing for the determination of the 54 strongly polar compounds. The 76 compounds were analyzed in multiple reaction monitoring (MRM) mode via electrospray ionization, and quantified by matrix matching external standard method. The results showed that the correlation coefficients were greater than 0.995, and the limits of quantification (LOQs) were lower than 10 μg/kg. The recoveries ranged from 61.3% to 96.2%, with the relative standard deviation (RSD) between 2.0% and 14.6%. The method was applied to 170 pork samples sold in the market, 23 samples of which were detected with 2 types of 5 veterinary drugs residues. The method was simple, rapid, accurate, reliable, and suitable for rapid screening and accurate detection of multiple veterinary drug residues in pork

Preparation and Performance of Antifouling PVC/CPVC Blend Ultrafiltration Membranes

Polyvinyl chloride (PVC) and chlorinated polyvinyl chloride (CPVC) were used as membrane materials to fabricate blend ultrafiltration membranes. Polyethylene glycol (PEG2000) and polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (Pluronic F127) were used as both pore forming agent and surface modifier to improve the permeability. The advantage of amphiphilic Pluronic F127 is that it enables higher -CH2-CH2-O- segment coverage on the membrane surfaces. The increase of CPVC proportion in membrane materials could improve the water fluxes of PVC/CPVC blend membranes with the slight change of protein rejection ratios. All the PVC/CPVC blend membranes with an additive of Pluronic F127 have excellent antifouling property. The blend method is an appropriate way to prepare new antifouling PVC/CPVC ultrafiltration membranes which have lower cost and better performance