Energy dependence on modes of electric activities of neuron driven by multi-channel signals

Nonlinear Dynamics - Neuron can receive electric signals or forcing currents from more than one channel, and these forcing currents could show some diversity. Based on the Hindmarsh–Rose...     

Sin-QuEChERS净化-超高效液相色谱-串联质谱法测定鱼肉中8种喹诺酮类药物残留量北大核心CSCD

将粉碎后的鱼肉样品2.00 g置于50 mL离心管中,加入100μg·L^(-1)内标溶液200μL和水5 mL,涡旋1 min后,用含5%(体积分数)乙酸的乙腈溶液10 mL超声提取10 min,加盐包(6 g无水硫酸镁、1.5 g氯化钠)使水相和乙腈相进行分层.涡旋、离心后,使用Sin-QuEChERS快速滤过柱直接插入离心管内,待提取液透过净化层上升至净化柱内时,移取5 mL提取液置于15 mL离心管内,加入体积比1∶1的乙腈-正己烷混合液5 mL,混匀静置,取上层正己烷层涡旋,离心,于40℃氮气吹至近干,用0.2%(体积分数)甲酸溶液定容至1 mL,过滤后上机UHPLC-MS/MS,在多反应监测模式下测定8种喹诺酮类药物的残留量.结果显示:该净化方法溶剂消耗降低至10 mL,前处理时间缩短至20~25 min.环丙沙星、培氟沙星、诺氟沙星、二氟沙星和达氟沙星标准曲线的线性范围均为1.00~500.0μg·L^(-1),检出限(3S/N)均为1.0μg·kg^(-1);氧氟沙星、恩诺沙星和沙拉沙星标准曲线的线性范围为0.50~500.0μg·L^(-1),检出限(3S/N)均为0.5μg·kg^(-1).用此法平行测定同一样品7次,测定值的相对标准偏差为1.3%~6.3%.按标准加入法进行回收试验,回收率为92.0%~108%.此法用于抽检兰州4家超市的3种鱼类,8种喹诺酮类药物均未检出,说明兰州市的鱼类食品中的药物残留问题相对安全.同时,与国家农业部1077号公告-1-2008中方法进行比对,测定结果基本一致.     

实时直接分析-串联质谱法快速筛查火锅底料、牛肉面汤及调味料中罂粟壳生物碱

建立了采用实时直接分析-串联质谱(DART-MS/MS)对火锅底料、牛肉面汤及调味料中5种非法添加的罂粟壳生物碱进行快速筛查的方法。样品经乙腈提取净化后,在离子化温度为300℃、栅极电压为150 V、进样速率为0.8 m m/s的DART离子源正离子模式条件下进样,以电喷雾离子源正离子多反应监测(MRM)模式进行检测,实现了样品经简单预处理后使用DART-MS/MS进行检测的新方法。该方法简便、快速,能满足大批量非法添加样品的快速筛查分析要求。     

Morphological characterization of the mouthparts of the vector leafhopper Psammotettix striatus (L.) (Hemiptera: Cicadellidae)

The leafhopper Psammotettix striatus (L.) (Hemiptera: Cicadellidae), is one of the most significant economic pests of wheat in Western China. This insect vectors a phytoplasma that causes wheat blue dwarf (WBD), a severe disease limiting wheat production in the Western China. A microscopic analysis of the ultrastructure of the mouthparts of the adult was conducted using scanning electron microscopy and the putative functions of the mouthparts were determined. The piercing-sucking mouthparts of P. striatus are of the conventional type comprising a three-segmented labium with a deep groove in the anterior side, a stylet fascicle consisting of two mandibular and two maxillary stylets, and an uppermost small cone-shaped labrum. The mandibular stylets, located laterad of the maxillary stylets, have sculpture on their tips, which may function in tearing plant tissue, cutting channels into the plant tissues, and attaching the body to the host plant during molting. The maxillary stylets are interlocked to form two separate compartments, a larger food canal and a smaller salivary canal. Two dendritic canals are also found in each maxilla and one in each mandible. Four kinds of sensilla were found on the labium: s. trichodea I, s. trichodea II, s. basiconic I, s. basiconic II. These may be involved in host recognition and are likely chemo- or mechanosensory, or both.     

Simulating the formation of spiral wave in the neuronal system

Some experimental results have confirmed that a spiral wave could be observed in the cortex of brain. The biological Hodgkin–Huxley neurons are used to construct a regular network with nearest-neighbor connection, artificial line defects are generated to block the traveling wave in the network, and the potential mechanism for formation of spiral wave is investigated. A target wave is generated in a local area by imposing two external forcing currents with diversity (I ₀?I ₁) in different areas of the network. It is confirmed that spiral wave could be induced by the defects even if no specific initial values are used. A single perfect spiral wave can occupy the network when the coupling intensity exceeds certain threshold; otherwise, a group of spiral waves emerges in the network. Certain channel noise can enhance the diversity (I ₀?I ₁) for generating target wave, and then spiral waves are induced by blocking the target wave with defects under no-flux and/or periodic boundary conditions in the network.     

Helical Substituted Polyacetylene‐Derived Fluorescent Microparticles Prepared by Precipitation Polymerization

This article reports the first fluorescent microparticles (MPs, approximately 600 nm in diameter) constructed using helical substituted polyacetylene and prepared via a precipitation polymerization approach. The MPs judiciously combine this interesting helical conjugated acetylene, fluorescent material and polymeric particles in one entity. The monomer containing a dansyl group undergoes precipitation polymerization in butanone/n‐heptane mixed solvent, with (nbd)Rh⁺B⁻(C₆H₅)₄ as a catalyst. MPs with a regular morphology are formed in a high yield (>80 wt%). UV‐vis spectroscopy demonstrates that the polymer chains making up the MPs adopt helical structures. The MPs show considerable fluorescence emission (λ_max, 500 nm; excited at 340 nm). Based on SEM and fluorescence images, the formation mechanism of the MPs is proposed. This methodology opens up new ways to prepare functional microstructured materials derived from substituted polyacetylenes, and may also result in opportunities for new practical applications of polyacetylene and its derivatives.

     

Real time band selective F1‐decoupled proton NMR for the demixing of overlay spectra of chiral molecules

The small chemical shift dispersion and complex multiplicity pattern in proton NMR limit quantifications, for instance the determination of enantiomeric excess (ee) for an enantiomeric mixture. Herein, we present a simple proton–proton correlation experiment with band selective homonuclear (BASH) decoupling in both F₁ and F₂ dimensions, for the removal of scalar and residual dipolar couplings to provide collapsed singlet for each chemical site. The method has been demonstrated to separate the severely overlapped spectra of enantiomers using both chiral isotropic and anisotropic phases as well as a small biomolecule, particularly for the diastereotopic protons and also for the determination of ee. Copyright © 2016 John Wiley & Sons, Ltd.