Imaging of wood tissue by ToF-SIMS: Critical evaluation and development of sample preparation techniques

Tissue of Norway spruce wood was investigated by time-of-flight secondary-ion mass spectrometry (ToF-SIMS) and field-emission scanning electron microscopy (FE-SEM). Different sample preparation techniques (including sectioning and drying) traditionally used for SEM analysis were compared and critically evaluated. A high contamination of wood surfaces by polytetrafluoroethylene (PTFE) introduced onto the sample during sectioning was detected by ToF-SIMS. A new protocol was developed and images of wood sections dried in different ways were compared. Main location of Mg, Na, K and Ca, but no lignin in membranes of bordered pits in spruce section surfaces was detected by ToF-SIMS imaging if critical point drying (CPD) or acetone extraction followed by drying under nitrogen flow (AEND) was applied. No specific locations of wood components as well as low signals from metal ions (Mg and Na) were observed on the wood surfaces of freeze-dried (FD) or air-dried (AD) sections. It was found that extractive substances, presenting on surfaces of FD and AD wood section, were evenly distributed on the surfaces and interfered with ToF-SIMS analysis. Our results indicated that ToF-SIMS imaging was critically sensitive to the sample preparation technique and a strict protocol for characterization of metals, lignin and polysaccharides in wood was suggested.     

Non‐vacuum field desorption ion source implemented under super‐atmospheric pressure

Standard field desorption (FD) ionization is implemented under high vacuum condition. In this paper, non‐vacuum FD is performed under a super‐atmospheric pressure environment using untreated tungsten wires as FD emitter, and the ion source was coupled to a commercial linear ion trap mass spectrometer. The operating pressure of the ion source was 6 bars which was high enough to provide sufficient dielectric strength to the working gas so that the high voltage that was required for FD could be applied to the emitter without occurrence of electrical discharge. Non‐volatile sample deposited on the bare tungsten wire FD emitter was heated by flowing direct current through the emitter. Similar to vacuum FD, the formation of conical protrusion of the liquefied sample layer under the strong electric field was also observed. Using the present ion source, high pressure field‐desorption of polar neutral compounds, organic salts and ionic liquids is demonstrated. Copyright © 2012 John Wiley & Sons, Ltd.     

CAN FD控制器中可变速率的实现

传统的CAN总线受环路延迟的影响,传输速率无法突破1Mbps.本文根据CAN FD协议标准与国际标准ISO11898,采用硬件描述语言verilog设计,实现了CAN FD控制器的可变速率功能.控制器采用状态机实现对数据帧的接收,采用改变组成bit位中最小时间单元tq的周期长度实现速率切换,并在数据帧的data域应用二...     

An overview of analytical methodologies for the determination of antibiotics in environmental waters

The widespread occurrence of antibiotics as contaminants in the aquatic environment has increased attention in the last years. The concern over the release of antibiotics into the environment is related primarily to the potential for the development of antimicrobial resistance among microorganisms. This article presents an overview of analytical methodologies for the determination of quinolone (Qs) and fluoroquinolone (FQs), macrolide (MLs), tetracycline (TCs), sulfonamide (SAs) antibiotics and trimethoprim (TMP) in different environmental waters. The analysis of these antibiotics has usually been carried out by high-performance liquid chromatography (HPLC) coupled to mass spectrometry (MS) or tandem mass spectrometry (MS/MS) and to a lesser extent by ultraviolet (UV) or fluorescence detection (FD). A very important step before LC analysis is sample preparation and extraction leading to elimination of interferences and prevention of matrix effect and preconcentration of target analytes.     

(FD)~2TD计算金属表面场增强

本文首次利用依赖于频率的时域有限差分法(FD)2TD来计算隐失波激励下金属粒子表面的场增强。首先,利用(FD)2TD计算了三维球形银粒子的表面场增强,与国外文献[11]中用不同方法对此问题的计算结果进行了对比,结果较为相符,说明我们自己编写的(FD)2TD程序是可信的。然后,利用此程序计算了在全内反射条件下,处于介质板上纳米尺度边长的正三角形银粒子表面的场增强,给出了该正三角形银粒子三角端点存在场增强的所谓"热点"并给出了该处的场增强值随样品距离的变化曲线。     

Limitation of immunoaffinity column for the removal of abundant proteins from plasma in quantitative plasma proteomics

In plasma proteomics, before a proteome analysis, it is essential to prepare protein samples without high‐abundance proteins, including albumin, via specific preparation techniques, such as immunoaffinity capture. However, our preliminary experiments suggested that functional changes with use alter the ability of the immunoaffinity column. Thus, in this study, to evaluate the changes of the removal ability of abundant proteins from plasma by the immunoaffinity column, plasma proteome analysis was performed for the long‐term test for the reproducibility of the affinity column using the fluorogenic derivatization–liquid chromatography–tandem mass spectrometry method combined with an IgY column. The specific adsorption for albumin decreased with an increase in the number of the column usage before its expiration date. Moreover, it was demonstrated that hydrophobic high molecular weight compounds in plasma adsorbed onto the column materials surface contributed to the functional changes from specific immunoaffinity adsorption into hydrophobic interaction. These results suggested that, in quantitative plasma proteomics studies, it is important to keep in mind the risk of not only the nonselective loss but also the changes in the adsorption ability of the immunoafinity column. Copyright © 2008 John Wiley & Sons, Ltd.     

Liquid phase microextraction applications in food analysis

Over the last years, liquid-phase microextraction (LPME) in its different application modes (single drop microextraction, dispersive liquid-liquid microextraction and hollow fiber-LPME) has been increasingly applied for the extraction of both inorganic and organic analytes from different matrices. Its advantages over conventional extraction procedures (simplicity, effectiveness, rapidity and low consumption of organic solvents) has also attracted its application in the complex food analysis field, in which it has clearly provided good and challenging results. A comprehensive review dealing with those articles published since its introduction till the end of March 2011 is presented, offering also a critical vision of the analytical potential of LPME for the analysis of foods.     

Asset pricing for an affine jump‐diffusion model using an FD method of lines on nonuniform meshes

We present a novel numerical scheme for the valuation of options under a well‐known jump‐diffusion model. European option pricing for such a case satisfies a 1 + 2 partial integro‐differential equation (PIDE) including a double integral term, which is nonlocal. The proposed approach relies on nonuniform meshes with a focus on the discontinuous and degenerate areas of the model and applying quadratically convergent finite difference (FD) discretizations via the method of lines (MOL). A condition for observing the time stability of the fully discretized problem is given. Also, we report results of numerical experiments.     

混合二肽的场解吸质谱

为了探索生物化学、生物医学中混合寡肽的分析问题,对未衍生的混合二肽场解吸质谱进行了研究(图1和图2)。在图1图2中出现了所有二肽的准分子离子[M+H]~+,除此外还出现了[2M+H]~+、[M_(AB)+H]~+、[M_(AC)+H]~+等集聚离子,这些集聚离子能用于进一步确定各个肽的分子量。     

基亏μC／OS-Ⅱ的高精度超声波测距系统设计

介绍一种以ARM处理器LPC2138为核心,采用超声波回波信号的A／D采样检测原理,实时测距,液晶屏显示的便携式系统。该系统利用ARM处理器处理速度快的优点,自行处理A／D采样速度。系统的测距范围在0．1-4．5m内,测量精度为1cm,实时性好,准确方便,有较高的推广价值。