全玻璃实心保偏光子晶体光纤的研制

设计并采用棒管法结合毛细管堆积技术制备了一种全玻璃材料的实心保偏光子晶体光纤,光纤端面测试结果表明,这种结构设计有效克服了传统光子晶体光纤制造过程中空气孔易于塌陷的困难,光纤微结构保持良好.采用剪断法测得在1550nm波长下光纤的传输损耗为6.84dB/m.测试了输出光的偏振度,结果表明该光纤具有较好的保偏特性,说明采用此方法研制具有高保偏性能且制作工艺简单的光子晶体光纤是可行的.     

T1 measurements incorporating flip angle calibration and correction in vivo

In this work, we propose a variable FA method that combines in vivo flip angle (FA) calibration and correction with a short TR variable FA approach for a fast and accurate T(1) mapping. The precision T(1)s measured across a uniform milk phantom is estimated to be 2.65% using the conventional (slow) inversion recovery (IR) method and 28.5% for the variable FA method without FA correction, and 2.2% when FA correction is included. These results demonstrate that the sensitivity of the variable FA method to RF nonuniformities can be dramatically reduced when these nonuniformities are directly measured and corrected. The acquisition time for this approach decreases to 10 min from 85 min for the conventional IR method. In addition, we report that the averaged T(1)s measured from five normal subjects are 900 +/- 3 ms, 1337 +/- 8 ms and 2180 +/- 25 ms in white matter (WM), gray matter (GM) and cerebral spinal fluid (CSF) using the variable flip angle method with FA correction at 3 T, respectively. These results are consistent with previously reported values obtained with much longer acquisition times. The method reduces the total scan time for whole brain T(1) mapping, including FA measurement and calibration, to approximately 6 min. The novelty of this method lies in the in vivo calibration and the correction of the FAs, thereby allowing a rapid and accurate T(1) mapping at high field for many applications.     

Multimodal investigations of trans-endothelial cell trafficking under condition of disrupted blood-brain barrier integrity

Background  

Stem cells or immune cells targeting the central nervous system (CNS) bear significant promises for patients affected by CNS disorders. Brain or spinal cord delivery of therapeutic cells is limited by the blood-brain barrier (BBB) which remains one of the recognized rate-limiting steps. Osmotic BBB disruption (BBBD) has been shown to improve small molecule chemotherapy for brain tumors, but successful delivery of cells in conjunction with BBBD has never been reported.     

Biomass‐derived Nitrogen and Phosphorus Co‐doped Hierarchical Micro/mesoporous Carbon Materials for High‐performance Non‐enzymatic H2O2 Sensing

Nitrogen and phosphorus co‐doped hierarchical micro/mesoporous carbon (N,P‐MMC) was prepared by simple thermal treatment of freeze‐dried okra in the absence of any other additives. The 0.96 wt % of N and 1.47 wt % of P were simultaneously introduced into the graphitic framework of N,P‐MMC, which also possesses hierarchical porous structure with mesopores centered at 3.6 nm and micropores centered at 0.79 nm. Most importantly, N,P‐MMC carbon exhibits excellent catalytic activity for electrocatalytic reduction of H₂O₂, resulting in a new strategy to construct non‐enzymatic H₂O₂ sensor. The N,P‐MMC‐based H₂O₂ sensor displays two linear detection range about 0.1 mM–10 mM (R²=0.9993) and 20 mM–200 mM (R²=0.9989), respectively. The detection limit is estimated to be 6.8 μM at a signal‐to‐noise ratio of 3. These findings provide insights into synthesizing functional heteroatoms doped porous carbon materials for biosensing applications.     

Development of an economic ultrafast liquid chromatography with tandem mass spectrometry method for trace analysis of multiclass mycotoxins in Polygonum multiflorum

Rapid, economic, and highly effective determination of multiple mycotoxins in complex matrices has given huge challenges for the analytical method. In this study, an economic analytical strategy based on sensitive and rapid ultrafast liquid chromatography coupled to hybrid triple quadrupole/linear ion trap mass spectrometry technique was developed for the determination of seven mycotoxins of different chemical classes (aflatoxin B₁, B₂, G₁, and G₂, ochratoxin A, T‐2 toxin, and HT‐2 toxin) in Polygonum multiflorum. Target mycotoxins were completely extracted using a modified quick, easy, cheap effective, rugged, and safe method without additional clean‐up steps. The types of extraction solvents and adsorbents for the extraction procedure were optimized to achieve high recoveries and reduce coextractives in the final extracts. Due to significant matrix effects for all analytes (≤68.9% and ≥110.0%), matrix‐matched calibration curves were introduced for reliable quantification, exploring excellent linearity for the seven mycotoxins with coefficients of determination >0.9992. The method allowed high sensitivity with limit of detection in the range of 0.031–2.5 μg/kg and limit of quantitation in the range of 0.078–6.25 μg/kg, as well as satisfactory precision with relative standard deviations lower than 8%. Recovery rates were between 74.3 and 119.8% with relative standard deviations below 7.43%. The proposed method was successfully applied for 24 batches of P. multiflorum samples, and six samples were found to be positive with aflatoxin B₁, B₂, G₁, or ochratoxin A. The method with significant advantages, including minimum analytical time, low time and solvent consumption, and high sensitivity, would be a preferred candidate for economic analysis of multiclass mycotoxins in complex matrices.     

Mesostructured cellular foam solid‐phase microextraction coating for the highly sensitive recognition of polychlorinated biphenyls in water samples

We herein presented a mesoporous cellular foam solid‐phase microextraction coating that showed highly sensitive recognition for weakly polarity polychlorinated biphenyls in water samples. The mesoporous cellular foam coater fiber was for the first time prepared by a simple sol‐gel method. The main experimental parameters including extraction temperature, extraction time, desorption time, stirring rate, and ionic strength were investigated by high‐efficiency orthogonal array design, a L₁₆ (4⁴) matrix was applied for the identification of optimized extraction parameters, and the optimized method was successfully applied to the analysis of environmental water sample. The novel mesoporous cellular foam coated fibers exhibited sensitive limits of detection (0.07–0.28 µg/L), wide linearity (5–3000 µg/L), and good reproducibility (3.5–8.3% for single fiber, and 4.9–8.7% for fiber‐to‐fiber) for polychlorinated biphenyls. The home‐made coating was successfully used in the analysis of polychlorinated biphenyls in real environmental water samples. These results indicate that the synthesized mesoporous cellular foams are promising materials for adsorption and separation applications in sample pretreatment.     

Inhibition of Inflammation‐Associated Thrombosis with ROS‐Responsive Heparin‐DOCA/PVAX Nanoparticles

Inflammation‐associated thrombosis is a non‐negligible source of mortalities and morbidities worldwide. To manipulate inflammation‐associated coagulation, nanoparticles that contain anti‐inflammatory polymer (copolyoxalate containing vanillyl alcohol, PVAX) and anti‐thrombotic heparin derivative deoxycholic acid (Hep‐DOCA) are prepared. The strategy takes advantage of the reducted side effects of heparin through heparin conjugation, achievement of long‐term anti‐inflammation by inflammation‐trigged release of anti‐inflammatory agents, and formation of PVAX/heparin‐DOCA nanoparticles by co‐self‐assembly. It is demonstrated that the Hep‐DOCA conjugate and PVAX are synthesized successfully; PVAX and Hep‐DOCA nanodrugs (HDP) are obtained by co‐assembly; the HDP nanoparticles effectively reduce the inflammation and coagulation without inducing lethal bleeding both in vivo and in vitro. The method provided here is versatile and effective, which paves new way to develop nanodrugs to treat inflammation‐associated thrombosis safely.     

基于瞬态光栅频率分辨光学开关法测量飞秒脉冲的研究

超宽光谱的飞秒脉冲测量一直是超快激光领域的重要研究方向之一.常规的飞秒脉冲自相关方法是通过测量自相关倍频信号来获得,而倍频信号具有波长选择性,不同中心波长的飞秒脉冲测量需要更换不同的倍频晶体,十分不方便.因此,提出了一种改进型的瞬态光栅频率分辨光学开关(TG-FROG)方法用于测量飞秒脉冲.该方法结合四波混频和频率分辨光学开关方法,其基本过程是将待测脉冲分为三束,其中两束脉冲经过精密的延时控制并聚焦在光学介质上达到时空重合,利用三阶非线性效应产生稳定的瞬态光栅作为开关光;另一束脉冲作为探测光与产生的瞬态光栅进行相互作用产生一个信号光,使用光谱仪对该信号光的光谱与延迟时间进行测量,并通过反演迭代算法处理而获取待测飞秒脉冲的光谱与电场信息.该方法只需要待测光的功率密度达到三阶非线性效应就可以实现测量,因此可以应用于任意中心波长的飞秒脉冲测量.利用该方法对中心波长分别为800 nm, 400 nm的飞秒脉冲,以及超连续亚10 fs的周期量级超宽光谱飞秒脉冲进行了测量,并与常规的干涉自相关仪器测量结果进行了比较,所得测量结果基本一致.实验结果表明,建立的基于TG-FROG方法对不同中心波长,不同脉冲宽度的飞秒脉冲测量是十分有效的.     

Removal of strontium from aqueous solutions by sodium dodecyl sulfate-modified palygorskite

Journal of Radioanalytical and Nuclear Chemistry - Palygorskite (PAL) was modified with sodium dodecyl sulfate (SDS) for the removal of Sr(II) from aqueous solutions. Analysis of the structural...     

Enantioselective Synthesis of 2‐Oxindole Spirofused Lactones and Lactams by Heck/Carbonylative Cylization Sequences: Method Development and Applications

An efficient one‐pot assembly of all‐carbon spiro‐oxindole compounds from non‐oxindole‐based materials has been developed through a palladium‐catalyzed asymmetric Heck/carbonylative lactonization and lactamization sequence. Diversified spirooxindole γ‐and δ‐lactones/lactams were accessed in high yields with good to excellent enantioselectivities (up to 99 % ee) under mild reaction conditions. The natural product coixspirolactam A was conveniently synthesized by applying the current methodology, and thus its absolute configuration was elucidated for the first time. Asymmetric synthesis of an effective CRTH2 receptor antagonist has also been demonstrated utilizing this method in the key step.