In vivo mechanical study of helical cardiac pacing electrode interacting with canine myocardium

Cardiac pacing is a medical device to help human to overcome arrhythmia and to recover the regular beats of heart. A helical configuration of electrode tip is a new type of cardiac pacing lead distal tip. The helical electrode attaches itself to the desired site of heart by screwing its helical tip into the myocardium. In vivo experiments on anesthetized dogs were carried out to measure the acute interactions between helical electrode and myocardium during screw-in and pull-out processes. These data would be helpful for electrode tip design and electrode/myocardium adherence safety evaluation. They also provide reliability data for clinical site choice of human heart to implant and to fix the pacing lead. A special design of the helical tip using strain gauges is instrumented for the measurement of the screw-in and pull-out forces. We obtained the data of screw-in torques and pull-out forces for five different types of helical electrodes at nine designed sites on ten canine hearts. The results indicate that the screw-in torques increased steplike while the torque–time curves presente saw-tooth fashion. The maximum torque has a range of 0.3–1.9 N mm. Obvious differences are observed for different types of helical tips and for different test sites. Large pull-out forces are frequently obtained at epicardium of left ventricle and right ventricle lateral wall, and the forces obtained at right ventricle apex and outflow tract of right ventricle are normally small. The differences in pull-out forces are dictated by the geometrical configuration of helix and regional structures of heart muscle.     

Stepwise Diagnostic Product Ions Filtering Strategy for Rapid Discovery of Diterpenoids in Scutellaria barbata Based on UHPLC-Q-Exactive-Orbitrap-MS

Diterpenoids are considered the major bioactive components in Scutellaria barbata to treat cancer and inflammation, but few comprehensive profiling studies of diterpenoids have been reported. Herein, a stepwise diagnostic product ions (DPIs) filtering strategy for efficient and targeted profiling of diterpenoids in Scutellaria barbata was developed using UHPLC-Q-Exactive-Orbitrap-MS. After UHPLC-HRMS/MS analysis of six diterpenoid reference standards, fragmentation behaviors of these references were studied to provide DPIs. Then, stepwise DPIs filtering aimed to reduce the potential interferences of matrix ions and achieve more chromatographic peaks was conducted to rapidly screen the diterpenoids. The results demonstrated that stepwise DPIs were capable of simplifying the workload in data post-processing and the effective acquisition of low abundance compounds. Subsequently, DPIs and MS/MS fragment patterns were adopted to identify the targeted diterpenoids. As a result, 381 diterpenoids were unambiguously or tentatively identified, while 141 of them with completely new molecular weights were potential new diterpenoids for Scutellaria barbata. These results demonstrate that the developed stepwise DPIs filtering method could be employed as an efficient, reliable, and valuable strategy to screen and identify the diterpenoid profile in Scutellaria barbata. This might accelerate and simplify target constituent profiling from traditional Chinese medicine (TCM) extracts.     

Parallel Split-Step Fourier Methods for Nonlinear Schrödinger-Type Equations

The nonlinear Schrödinger equation is of tremendous interest in both theory and applications. Various regimes of pulse propagation in optical fibers are modeled by some form of the nonlinear Schrödinger equation. In this paper we introduce sequential and parallel split-step Fourier methods for numerical simulations of the nonlinear Schrödinger-type equations. The parallel methods are implemented on the Origin 2000 multiprocessor computer. Our numerical experiments have shown that these methods give accurate results and considerable speedup.     

Glycosylthiomethyl chloride: a new species for S-neoglycoconjugate synthesis. Synthesis of 1-N-glycosylthiomethyl-1,2,3-triazoles

Reaction of O-acyl-protected glycosylthiols with dichloromethane afforded readily glycosylthiomethyl chlorides, which gave with sodium azide the corresponding glycosylthiomethyl azides 17-22. Reaction of these azides with dicyclopentadiene as dipolarophile led to tandem 1,3-dipolar cycloaddition/retro-Diels-Alder reaction furnishing the parent 1-glycosylthiomethyl-1,2,3-triazoles 23-25. Reaction of azides with acetylene derivatives gave directly 1-glycosylthiomethyl-1,2,3-triazoles which are ring-substituted.     

界面张力在基板诱导共混物分散相粒子粗化生长加速现象中的作用

通过相差显微镜和计算机图像处理来研究两相聚合物体系的粗化过程 .将具有不同聚比的乙烯 聚醋酸乙烯酯 (EVAc)共聚物与聚丙烯 (PP)共混 ,制备不同相界面张力的系列共混物薄膜 .观察了在玻璃基板的作用下 ,不同界面张力体系的分散相粒子粗化行为 ,发现界面张力在约 0 4 8·1 0 - 5N cm以上的体系中分散相粒子的粗化有明显的加速现象 ,粒子体积生长与时间关系的指数大于 1 0 ;而两相界面张力较低的情况下 ,选择具有不同表面极性的基板对同一体系试验 ,我们均未发现有粗化加速现象产生 ,且采用不同基板之间的试验结果差异很小 ,亦即当高分子共混物的相界面张力大于一定值时 ,仅与基板存在有关 ,粒子的粗化行为被加速     

Preparation of P(AN–MMA) microporous membrane for Li-ion batteries by phase inversion

A novel process was proposed for preparation of microporous poly(acrylonitrile–methyl methacrylate) (P(AN–MMA)) membranes by phase inversion techniques using ultrasonic humidifier. Being prepared by dissolving the polymer (PAN–MMA) in the N,N-dimethylformamide (DMF) solution with mechanical stirring, the homogenous casting solution was cast onto a clean glass plate. Successively, the glass plate was exposed to the water vapor produced by ultrasonic humidifier, inducing the phase inversion. It is found the pore size is much more uniform across the cross-section of the membrane than that of the porous membrane prepared by conventional water bath coagulation technique. The microporous membranes were directly obtained after the washing and drying. It had about 1–5 μm of pores and presented an ionic conductivity of 2.52 × 10⁻³ S/cm at room temperature when gelled with 1 M LiPF₆/EC-DMC (1:1 vol.%) electrolyte solution. The test cells with the gel electrolytes prepared from as-prepared microporous membranes showed stable cycling capacities, indicating that the microporous membrane, which was prepared from cheap starting materials acrylonitrile and methyl methacrylate, can be used for the gel electrolyte of lithium batteries.     

希土硝酸盐冠醚Yb(NO3)3·3H2O/B15C5配合物的研究

用改进的半微量相平衡方法研究了Yb(NO_3)_3·3H_2O-Bl5C5-CH_3COCH_3三元体系在18℃时的溶解度,测定了各液相的折光率。结果指出只有一种化学计量的配合物(Yb(NO_3)_3·B15C5·3H_2O·2CH_3COCH_3)生成。分离、洗涤、浓硫酸干燥器中恒重后,经化学分析,确定配合物的组成为:Yb(NO_3)_3·B15C5·3H_2O·065CH_3COCH_3。用红外光谱、DTG、TG及DSC等对配合物进行了研究。测得配合物的脱溶剂与热分解的热焓值(△H)。按照Kissinger法,求得配合物热分解过程的表现活化能。     

生物体中微量钛的测定——邻硝基苯基荧光酮直接光度法

研究了用邻硝基苯基荧光酮显色测酞时,酒石酸钾钠和氟化铵的影响。从而能直接测定生物体中微量钛。检出限为0.05μg.     

Fluorescent Probes for Live Cell Thiol Detection

Thiols play vital and irreplaceable roles in the biological system. Abnormality of thiol levels has been linked with various diseases and biological disorders. Thiols are known to distribute unevenly and change dynamically in the biological system. Methods that can determine thiols’ concentration and distribution in live cells are in high demand. In the last two decades, fluorescent probes have emerged as a powerful tool for achieving that goal for the simplicity, high sensitivity, and capability of visualizing the analytes in live cells in a non-invasive way. They also enable the determination of intracellular distribution and dynamitic movement of thiols in the intact native environments. This review focuses on some of the major strategies/mechanisms being used for detecting GSH, Cys/Hcy, and other thiols in live cells via fluorescent probes, and how they are applied at the cellular and subcellular levels. The sensing mechanisms (for GSH and Cys/Hcy) and bio-applications of the probes are illustrated followed by a summary of probes for selectively detecting cellular and subcellular thiols.     

A simple and efficient synthesis of 2-aryl-substituted benzimidazoles

Sodium hydrogen sulfite was used to promote condensation of o-phenylenediamine with aromatic aldehydes in dimethylformamide to obtain the corresponding 2-arylbenzimidazoles. The procedure is simple and convenient, and it implies inexpensive promoter and is characterized by short reaction time and easy purification of the final products. Published in Russian in Zhurnal Organicheskoi Khimii, 2008, Vol. 44, No. 6, pp. 872–874. The text was submitted by the authors in English.