Simultaneous HPLC quantification of total cholesterol,tocopherols and β-carotene in Barrosã-PDO veal

A simple, rapid and sensitive procedure for the simultaneous determination of total cholesterol, tocopherols and β-carotene in meat is described. The method involves a direct saponification of the meat, a single n-hexane extraction and the analysis of the extracted compounds by normal-phase HPLC, using fluorescence (tocopherols) and UV–Vis photodiode array (cholesterol and β-carotene) detections in tandem. Rates of recovery of spiked meat samples were 93% for cholesterol, 83–86% for (α-, β- and -γ) tocopherols and 89% for β-carotene. Repeatabilities were high (CV < 6%) for all determined compounds, except for δ-tocopherol. This tocopherol, which is not usually present in meat, showed a much lower recovery percentage (73%) and repeatability (12.8%). This methodology was applied for the quantification of total cholesterol, tocopherols and β-carotene in three muscles (longissimus thoracis, longissimus lumborum and semitendinosus) of the Portuguese traditional Barrosã-PDO veal, obtained from autochthonous calves fed extensively during summer (with the least abundant green pastures) and slaughtered in early autumn (October). Barrosã-PDO veal showed median contents of total cholesterol (0.50–0.56 mg/g) and, depending on the analysed muscle, moderate to high contents of α-tocopherol (3.3–3.9 μg/g) and β-carotene (0.07–0.09 μg/g), suggesting an high sensorial and hygienic quality.     

Effect of functional group of ferrocene redox substance on the transport properties of newly designed ion exchange membrane prepared from polymer gel

A different newly designed cationic exchange polymer membrane and anionic exchange polymer membrane were introduced, and also the transport properties of these polymeric membranes were investigated in this study. The transport properties of these polymer membranes in contact with ferrocene redox derivatives were estimated by using electrochemical techniques such as cyclicvoltammetry, chronopotentiometry, and chronoamperometry techniques, respectively. The used ferrocene redox substances, which have different functional groups, were (Ferrocenylmethyl) trimethylamonium iodide, FcMA, Ferrocenedimethanol, FcDM, and Ferrocene carboxylic acid, FcCA. It indicated that the performance of a membrane depended on the content of polymer gel, anionic exchange polymer site (20 wt % and 50 wt %) or cationic polymer exchange site (20 wt % and 50 wt %), and the efficiency of the functional groups of cationic and anionic exchange polymer site as well. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

一种新的知觉分割模型*

根据知觉的最新理论研究和实验结果,提出一种新的知觉模型,并用于考查计算机视觉中的分割问题.分割问题实质上是知觉表达问题,现在分割的困难性可能是知觉上局部到整体的还原论假设造成的;分割可能不是一次完成的,而是经过整体到局部的过程才最终完成.新的知觉模型将对建立更好的分割模型提供理论基础.     

Critical evaluation of coupling particle size distribution with the shrinking core model

The shrinking core model (SCM) is widely used to model fluid-solid reactions such as the leaching of metals from minerals. In most cases, however, the particle size distribution (PSD) of the solid material was disregarded. In this paper the erroneous shift in the control regime when neglecting PSD was quantified and the dependence of the shift on the coefficients of variation (CV) and the type of PSD was analysed. By coupling the SCM with a Gamma PSD, it was found that neglecting the PSD would shift the control regime from chemical reaction to inert/ash layer diffusion, when the CV was between 0.7 and 1.2. For a system controlled by liquid film diffusion, neglect of the PSD, would shift the control regime to chemical reaction when CV is between 0.3 and 0.7 or to inert/ash layer diffusion when CV is greater (0.9-1.5). It was therefore postulated that some researchers had unknowingly made invalid conclusions about the control regime due to the neglect of PSD. However, an inert/ash layer diffusion-controlled process was insensitive to the neglect of PSD. When CV<0.3, neglect of the PSD would not cause any erroneous shifts, irrespective of the control regime. Experimental data confirmed the observation. For a given CV, the deviation in the fraction reacted from the mono-PSD increases with CV and decreases with time. The maximum deviation, which occurs at the beginning, is about 10% with a gamma PSD of CV=0.3. The percent deviation is dependent of the type of PSDs. Gamma PSD gives the lowest deviation while Gaudin-Schuhmann results in the largest deviation (maxi. ∼19%, with CV=0.3) in the first half of dissolution process. Log-normal distribution gives a larger deviation than gamma but quickly approaches the latter with time. The deviation for Rosin-Rammler is between log-normal and Gaudin-Schuhmann. For systems with CV less than 0.3, the SCM can be fairly used without considering PSD. When CV is greater than 0.3, particularly in the early stage of a dissolution process with a PSD other than gamma, PSD should be included to avoid substantial errors.     

Tribological behavior of plasma spray coatings for marine diesel engine piston ring and cylinder liner

High-temperature wear characteristics between plasma spray coated piston rings and cylinder liners were investigated to find the optimum combination of coating materials using the disc-on-plate reciprocating wear test in dry conditions. The disc and plate represented the piston ring and the cylinder liner, respectively. Coating materials studied were Cr₂O₃-NiCr, Cr₂O₃-NiCr-Mo, and Cr₃C₂-NiCr-Mo. Plasma spray conditions for the coating materials were established adjusting stand-off distance to obtain a coating with a porosity content of ∼5%. It was found that a dissimilar coating combination of Cr₂O₃-NiCr-Mo and Cr₃C₂-NiCr-Mo provided the best antiwear performance. The addition of molybdenum was found to be beneficial to improve the wear resistance of the coating. Hardness differences between mating surfaces were also important factors in determining the wear characteristics, so that it should be controlled below 300 in Vickers hardness under dry conditions. Adhesive wear accompanying with metal transfer was a dominant wear mechanism for dry conditions.     

The fabrication of functional biosurface composed of iron storage protein, ferritin

A functional biosurface applicable to a biomemory device was fabricated using ferritin, which is one of the globular protein complexes consisting of 24 protein subunits, which can be classified as metalloproteins. For the fabrication of uniform ferritin layer, 11-MUA(11-mercaptoundecanoic acid) was used as a linker material. The formation of the ferritin layer was confirmed by surface plasmon resonance (SPR) spectroscopy, and the morphology of the immobilized ferritin was analyzed by scanning tunneling microscopy (STM). The electrochemical redox property investigation was accomplished by the cyclic voltammetry (CV) technique. These results of adsorbed ferritin on the modified electrode can be used for the fabrication of bioelectronics.     

纳米Au修饰电化学传感器检测沙林机理的研究

采用Raman光谱和循环伏安法研究了纳米A以u电极检测沙林的电化学反应机理。研究发现,以Fe“作为检测沙林分子中F的探针离子、纳米Au修饰的Au电极电化学传感器检测液相中的沙林,可同时检测到沙林分子中F和P=0基团,实验结果具备特征性。     

Aptamer biosensor for label-free impedance spectroscopy detection of thrombin based on gold nanoparticles

This paper presents a simple electrochemical impedance spectroscopy (EIS) aptasensor based on an anti-thrombin-aptamer as a molecular recognition element. Improvement in sensitivity was achieved by utilizing gold nanoparticles (AuNPs), which were self-assembled on the surface of a bare electrode by using 1,6-Hexanedithiol as a medium. To quantify the amount of thrombin, changes in the interfacial electron transfer resistance (R_et) of the aptasensor were monitored using the redox couple of an [Fe(CN)₆]^3−/4− probe. The plot of (Reti−Ret₀)/Ret₀ against the logarithm of thrombin concentration is linear with over the range from 0.1 nM to 30 nM with a detection limit of 0.013 nM. Meanwhile, the packing density of aptamers was determined by cyclic voltammetric (CV) studies of redox cations (e.g., [Ru(NH₃)₆]³⁺) which were electrostatically bound to the DNA phosphate backbones. The results indicate that the total amount of aptamer probes immobilized on the gold nanoparticle surface is sixfold higher than that on the bare electrode. The aptasensor also showed good selectivity for thrombin without being affected by the presence of other proteins.     

基于LS-SVR的压力传感器温度自补偿策略

硅压阻式压力传感器在实际使用过程中受环境温度影响易发生温度漂移,同时传感器本身又存在一定的非线性,这使得传感器测量精度大幅度降低.针对传统的温度补偿方法中需引入温度传感器的情况,提出一种基于最小二乘支持向量回归(LS-SVR)的压力传感器温度自补偿策略,通过定义并测量传感器桥路自身参数获取温度信息实现温度补偿,而无需配置额外的温度传感器.通过粒子群算法和交叉验证对LS-SVR的参数进行了优化.实验结果表明:这种利用传感器自身桥路进行温度补偿的方法能够有效地消除压力传感器的温度漂移.补偿后测量精度达到0.1%FS.     

基于EKF的机动目标跟踪算法的研究

假设一种机动目标运动:目标的速度大小不变,方向一直对准观测站.比较Singer模型和常速度(CV)模型,采用扩展卡尔曼滤波(EKF)算法对目标进行跟踪.仿真结果表明,在这种机动目标跟踪中,采用Singer模型比CV模型具有较快的收敛速度,而采用CV模型比Singer模型具有较高的跟踪精度.