Selective turn-on fluorescence detection of Vibrio parahaemolyticus in food based on charge-transfer between CdSe/ZnS quantum dots and gold nanoparticles

Vibrio parahaemolyticus (V. parahaemolyticus) is one of the most common food-borne pathogens found along the east coast of China, Japan, and several southeast Asian countries, where marine foods are frequently consumed. Thus it is of great interest to establish a fast, sensitive and robust analytical assay for V. parahaemolyticus detection. Herein, we report a V. parahaemolyticus-specific egg yolk antibody (IgY), extracted from the egg yolks of immunized hens with inactivated V. parahaemolyticus bacteria. By immobilizing IgY onto the surface of gold nanoparticles (AuNPs) through electrostatic self-assembly, a detection system was developed based on charge-transfer quenching fluorescence, which contains core/shell CdSe/ZnS quantum dots (QDs), IgY-AuNPs and free AuNPs. In this strategy, the IgY-AuNPs were induced to aggregate quickly in the presence of target V. parahaemolyticus, resulting in a rapid fluorescence response of the QDs. More importantly, the convenient turn-on fluorescent detection system exhibited excellent selectivity over the other bacteria. Furthermore, this facile one-step method can detect V. parahaemolyticus at low concentrations of 10 cfu/mL without pre-enrichment and can be applicable for the detection of V. parahaemolyticus in real food samples. With the advantage of simplicity, rapidness, sensitivity, and specificity, this proposed approach shows promise as a successful application of V. parahaemolyticus in bioanalysis.     

Gold nanoparticles-based lateral flow immunoassay with silver staining for simultaneous detection of fumonisin B1 and deoxynivalenol

A lateral flow immunoassay with silver staining for the simultaneous detection of fumonisin B₁ (FB₁) and deoxynivalenol (DON) in maize samples was reported. The assay was based on the competition between target mycotoxins and corresponding coating antigens immobilized on test lines for binding to limited gold nanoparticles (AuNPs)-labeled antibodies. The detection signal was further amplified by employment of silver staining on AuNPs. In the process, silver ions were catalyzed by AuNPs into metal silver that deposited on the surface of AuNPs, allowing not only the enlargement of particle dimensions of AuNPs but also a more distinguishable black coloration on the test zone. Under optimized conditions, the cut-off values of silver staining lateral flow immunoassay were 2.0 ng mL⁻¹ for FB₁ and 40 ng mL⁻¹ for DON in buffer, which was improved at least 2 times in comparison to those of AuNPs-based method. The assay was further applied to detect FB₁ and DON in naturally contaminated maize samples and a good agreement was found with the data obtained from HPLC-MS/MS.     

Highly sensitive electrochemical determination of sunset yellow in commercial food products based on CHIT/GO/MWCNTs/AuNPs/GCE

Sunset yellow (SY) belongs to the azo group, commonly used in food industry. Highly consumption of SY may lead toxicity and photogenic to human health. Herein, a simple and highly sensitive electrochemical sensor was developed based on the modified glassy carbon electrode (GCE) with graphene (GO), multiwall carbon nanotubes (MWCNTs), gold nanoparticles (AuNPs) and nanocomposite membrane of chitosan (CHIT) for quantifying the level of SY in commercial food products. The CHIT/GO/MWCNTs/AuNPs were coated onto the GCE surface and analysed by using differential pulse voltammetry (DPV). The surfaces of CHIT/GO/MWCNTs/AuNPs/GCE characteristics were observed under scanning electron microscopy and transmission electron microscope. Under optimal condition, the DPV method was sensitively detected with different concentrations of SY from 10 to 90 mg mL⁻¹. The limits of detection and quantification were obtained to be 0.032 mg mL⁻¹ and 0.096 mg mL⁻¹, respectively. The proposed method was successfully applied to quantify the amount of SY in candy, jelly and soft drinks with good recovery values from 98.11% to 104.03%. Hence, the proposed sensor shows a rapid and sensitive method, low cost and simple, which an appropriate for alternative technique use for the analysis of food colorants in commercial products.     

A simple and rapid biosensor for ochratoxin A based on a structure-switching signaling aptamer

A fast and reliable sensing platform has been developed for the detection of mycotoxin ochratoxin A (OTA) based on a target-induced structure-switching signaling aptamer. In the absence of target, a fluorescein-labeled OTA aptamer hybridizes to a complementary DNA strand containing a quencher moiety, bringing the fluorophore and the quencher into close proximity for highly efficient fluorescence quenching. Upon OTA addition, a conformational change in the aptamer releases the quencher-containing DNA strand, generating a strong concentration-dependent fluorescent signal. Using this technique, the entire detection and analysis process of OTA can be completed within 1 min. Under optimized assay conditions, a wide linear detection range (from 1 to 100 ng/mL) was achieved with a detection limit down to 0.8 ng/mL. Additionally, the proposed assay system exhibited high selectivity for OTA against other mycotoxins (aflatoxin B₁ and zearalenone) and limited interference from the structural analog ochratoxin B. The biosensor was also applied to a non-contaminated corn material spiked with a dilution series of OTA, obtaining recoveries from 83% to 106%. Utilization of the proposed biosensor for quantitative determination of mycotoxins in food samples may provide significant improvements in quality control of food safety through a simple, rapid, and sensitive testing system for agricultural products monitoring.     

Determination of melamine in infant formulas by fluorescence quenching based on the functionalized Au nanoclusters

An environmentally benign and cost-effective assay was developed for the fast determination of melamine (MA) with tiopronin-stabilized gold nanoclusters (TPN-AuNCs) as a fluorophore. The TPN-protected gold nanoclusters which exhibit strong fluorescence emission were prepared by a simple one-vessel procedure. Upon addition of melamine to TPN-AuNCs, a dramatic decrease in their fluorescence intensity was observed, attributing to the electrostatic attraction between the MA and the surface of the TPN-AuNCs which induces the aggregation of TPN-AuNCs. Parameters affecting the detection of MA were investigated including pH, amount of TPN-AuNCs, temperature as well as reaction time. Under the optimized experimental conditions, trace amounts of MA could be analyzed based on the reduction in the fluorescence intensity of TPN-AuNCs. A linear relationship was established at concentrations ranging from 0.09 μM to 100 μM. The detection limit at 32 nM was achieved for this method. The developed method has been successfully applied to the determination of MA in several spiked infant formulas samples purchased from a local supermarket. Excellent recoveries at 92.0–102.2% and precision (RSD: 1.14–2.80%) were attained, respectively, which confirmed the great potential of tiopronin-stabilized gold nanoclusters toward practical measurement of melamine in infant formulas of samples.     

聚苯胺负载纳米金催化剂的研究进展

综述了聚苯胺(PANI)负载纳米金催化剂的制备方法,包括PANI载体的合成及负载纳米金颗粒(AuNPs)的方法,介绍了PANI的不同形貌和AuNPs的不同空间负载位置对AuNPs的稳定性及催化活性的影响,分析了AuNPs吸附和原位还原两种不同负载方式的机理及优缺点,探讨了PANI与负载的AuNPs之间电荷转移和相互作用...     

Screening for β-agonists in sheep urine and eyes by an enzyme-linked immunosorbent assay in the state of Kuwait

Data are reported here on the assessment of the potential use of an enzyme-linked immunosorbent assay (ELISA) to monitor the presence of the β-agonist, clenbuterol in 142 samples of sheep urine and 53 samples of eye tissues from the same sheep. Data obtained showed that the clenbuterol levels ranged in the urine and eye tissues from not detected to 0.272 ppb and not detected to 1.54 ppb tissue, respectively. For confirmation, all samples that showed to be ELISA positive for clenbuterol residues were analyzed by GC–MS and were all found to be negative.     

Synchronous fluorescence and multivariate classification analysis as a screening tool for determining Sudan I dye in culinary spices

Spices are a globally traded commodity which has been found to be adulterated with forbidden Sudan dyes. This work proposes a screening method for determining the adulteration of paprika varieties (mild, hot and smoked) with Sudan I dye, based on constant-wavelength synchronous fluorescence spectroscopy with multivariate classification. Different wavelength-intervals (Δλ) were evaluated. Classification models were built with Partial Least Squares-Discriminant Analysis (PLS-DA) at two Sudan I dye concentration levels (1 and 5 mg L⁻¹) and they were tested with samples at a lower level (0.5 mg L⁻¹). Classification results were quite satisfactory when a strategy based on first-derivative spectra was used for improving classification results. Δλ = 60 nm was chosen as the optimum wavelength interval giving a 100% of sensitivity and specificity. These results are promising because the risk of assigning adulterated samples as safe to be consumed is highly minimized. The proposed method is feasible, rapid and simple taking advantage of Sudan I fluorescence phenomena in a direct way.     

可逆性吸脱附材料用于气相色谱法测定喷气燃料中芳烃含量

为提高喷气燃料中芳烃含量测定的准确性、精密度和分析速率,解决荧光指示剂吸附法面临的荧光指示剂供应问题,提出采用气相色谱(GC)快速测定喷气燃料中芳烃总量的方法.通过制备芳烃可逆性吸脱附材料,并将其用于气相色谱柱固定相,实现了喷气燃料中饱和烃与芳烃的气相色谱分离.该气相色谱法的芳烃测定结果与芳烃配制结果相关系数达到0.9...     

Determination of avermectin and milbemycin residues in bovine muscle by liquid chromatography-tandem mass spectrometry and fluorescence detection using solvent extraction and low temperature cleanup

A simple and inexpensive sample preparation method based on solvent extraction, followed by low temperature cleanup, was demonstrated to be applicable for the determination of avermectin and milbemycin residues in bovine muscle by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and liquid chromatography with fluorescence (LC-FL) detection. The analytical methodology was validated according to the Commission Decision 2002/657/EC, using LC-MS/MS for confirmatory and LC-FL for quantitative purposes. Mean recovery was between 88.9 and 100.7% in three distinct concentrations. The coefficient of variation for repeatability and within-laboratory reproducibility ranged from 0.78 to 5.1% and from 0.28 to 9.0%, respectively. Method precision led to satisfactory values of decision limits (CCα) and detection capabilities (CCβ). The proposed method has been applied in the Brazilian National Residue Control Plan since 2010 for the determination of avermectins and milbemycin residues in bovine muscle samples. A total of 760 samples were analyzed and none of them presented residues at concentrations above the permitted levels established by the more recently applied directives.     

全域正则化快速匹配追踪稀疏地震反演方法

匹配追踪算法(MP)自提出以来便被广泛应用于信号处理领域。文中首先利用时频域褶积算子与初始模型约束构建匹配追踪的冗余字典,在全时频域内筛选出所有可能的匹配原子构成备选原子库;然后利用正则化方法从备选原子库中筛选出能量最大的子集构成最终的匹配原子库,即一次迭代即可筛选出多个匹配原子。据此形成的上述全域正则化快速匹配追踪算法具有计算效率高、鲁棒性强等优点。此外,将初始模型约束与时频域联合反演方法引入反演框架,可有效提高反演结果的精度。对所提方法进行的一维、二维模型及三维实际资料的测试结果表明,全域正则化快速匹配追踪地震反演方法相较于常规匹配追踪的计算效率得到明显提高,反演结果既具有良好的鲁棒性,同时拥有较好的层位边界保真度。     

Modeling Asphaltene Precipitation Under Gas Injection and Pressure Depletion Conditions

Asphaltene precipitation is a major problem during primary oil production and enhanced oil recovery in the petroleum industry. In this work, a series of experiments was carried to determine the asphaltene precipitation of bottom hole live oil during gas injection and pressure depletion condition with Iranian bottom hole live oil sample, which is close to reservoir conditions using high pressure-high temperature equilibrium cell. In the majority of previous works, the mixture of recombined oil (mixture dead oil and associated gas) was used which is far from reservoir conditions. The used pressure ranges in this work covers wide ranges from 3 to 35 MPa for natural depletion processes and 24–45 MPa for gas injection processes. Also, a new approach based on the artificial neural network (ANN) method has been developed to account the asphaltene precipitation under pressure depletion/gas injection conditions and the proposed model was verified using experimental data reported in the literature and in this work. A three-layer feed-forward ANN by using the Levenberg-Marquardt back-propagation optimization algorithm for network training has been used in proposed artificial neural network model. The maximum mean square error of 0.001191 has been found. In order to compare the performance of the proposed model based on artificial neural network method, the asphaltene precipitation experimental data under pressure depletion/gas injection conditions were correlated using Solid and Flory-Huggins models. The results show that the proposed model based on artificial neural network method predicts more accurately the asphaltene precipitation experimental data in comparison to other models with deviation of less than 5%. Also, the number of parameters required for the ANN model is less than the studied thermodynamic models. It should be noted that the Flory and solid models can correlate accurately the asphaltene precipitation during methane injection in comparison with CO₂ injection.     

Results of acidizing injection wells on the Zhetybai field (Kazakhstan)

The article discusses the results of local acid treatment of key wells situated in the selected area of the deposit. This technique allows not only to recover well injection capacity, but also to increase the area sweep efficiency both according to the formation thickness and its strike, which helps to increase oil recovery.The method for effectiveness evaluation of the deposit stimulation technique has been proposed. It is based on calculation of formation system hydrodynamic characteristics with the account of well interference. Based on the geophysical well logging data (GWL), the area sweep efficiency is determined in accordance with the formation area and thickness.The proposed method has been implemented on the basis of the data of the Zhetybai (Kazakhstan) deposit.     

利用状态方程计算石油馏分相平衡的连续热力学方法

对石油馏分的相平衡计算，传统的方法是采用虚拟组分，利用状态方程进行求解。针对石油馏分组成复杂，沸点互相重叠交叉严重的特点，提出了直接利用馏分实沸点蒸馏曲线作为分布函数进行混合物相平衡计算的连续热力学方法。     

现场油基钻井液固相粒度评价新方法

固相颗粒分布对油基钻井液的性能影响较大,因此确定现场钻井液固相颗粒尺寸,对于调控钻井液性能具有重要意义。根据现场油基钻井液经固控设备分离前后的粒度分布数据,建立了固控设备清除效率与固相颗粒粒径分布关系。现场通过钻井液固相含量测定,可知现场固控设备的固控效率,进一步可确定现场钻井液固相颗粒粒径的分布范围。现场井浆固相含量测定表明,固控设备清除效率与固相颗粒粒径分布具有强相关性,相关系数R²可达0.97;经固控设备分离后,现场油基钻井液的固相含量由45.0%降至16.2%,清除效率达0.64。采用上述测试方法测得的固相粒径为12.50μm,在使用激光粒度分布仪得的粒径峰(7.11～12.73μm)范围内,表明该测试方法具有良好的准确性,可用于现场测量钻井液内的固相粒度。     

双谱特征荧光强度比值法在定量荧光录井中的应用

在钻井液污染条件下,准确、快速判别原油荧光显示是定量荧光录井技术的关键。为了寻找一种更科学、实用的技术方法,使该技术向更成熟和完善的程度发展,该文在国内外大量资料调研和室内实验、研究的基础上,首次提出了用于原油荧光显示识别的双谱特征荧光强度比值法。该方法综合提取了发射和同步荧光光谱的多重荧光信息,并利用新研制的原油荧光显示识别分析软件对信息进行智能化分析处理。该方法克服了当前定量荧光录井技术中岩样预处理过程带来的原油荧光信息损失,避免了背景扣除法的偏差。室内模拟实验和现场应用表明,该方法简便、快捷、准确,原油荧光发现率高。     

Seismic fluid identification using a nonlinear elastic impedance inversion method based on a fast Markov chain Monte Carlo method

Elastic impedance inversion with high efficiency and high stability has become one of the main directions of seismic pre-stack inversion. The nonlinear elastic impedance inversion method based on a fast Markov chain Monte Carlo (MCMC) method is proposed in this paper, combining conventional MCMC method based on global optimization with a preconditioned conjugate gradient (PCG) algorithm based on local optimization, so this method does not depend strongly on the initial model. It converges to the global optimum quickly and efficiently on the condition that efficiency and stability of inversion are both taken into consideration at the same time. The test data verify the feasibility and robustness of the method, and based on this method, we extract the effective pore-fluid bulk modulus, which is applied to reservoir fluid identification and detection, and consequently, a better result has been achieved.     

基于旋流和引射循环技术的湿气气液分离方法研究

天然气除湿对于天然气的安全输送和精确计量具有重要的意义。针对传统的湿气气液分离装置存在分离效率低、受流型影响大等问题,提出了一种基于旋流和引射循环技术的湿气气液分离装置和方法。通过室内实验的方法,对不同工况下的气液分离效率及压降特性等进行了研究。研究结果表明:①当表观气速为4.2~28.5 m/s、液相体积分数小于3%时,设计的气液分离装置的气液分离效率基本可维持在96%以上,压降最大为167 kPa;②随着气量的增大,气液分离装置的分离效率降低,压降增大;③湿气的液量对分离效率和压降的影响较小。上述研究结果可为工业生产中湿气的气液分离提供一种新的思路,具有重要的工程意义。      

Targeted approach for qualitative screening of pesticides in salmon feed by liquid chromatography coupled to traveling-wave ion mobility/quadrupole time-of-flight mass spectrometry

The current work reports the development and validation of a qualitative screening method for 156 pesticides in Atlantic salmon feeds based on the use of ultrahigh-performance liquid chromatography (UHPLC) coupled to traveling-wave ion mobility spectrometry (TWIMS)/quadrupole time-of-flight mass spectrometry (QTOFMS). This novel hyphenation allows a straightforward estimation of the collision cross section (CCS), a physicochemical property that recently has been proposed as an additional identification point for pesticides.In order to increase the overall efficiency of the screening workflow, data processing parameters and tolerances involved in the automated analyte detection were first optimized. The use of the CCS as an additional identification point greatly improved the method selectivity, decreasing the rate of false-positive detections in blank feed samples. Qualitative validation was then performed in accordance with the EU document SANTE/11945/2015 on analytical quality control and validation procedures for pesticide residues analysis in food and feed. Feed samples were spiked with 156 pesticides at three levels (0.01, 0.05 and 0.20 mg/kg) and analyzed by the proposed method. Under the optimized conditions, screening detection limits (SDLs) ≤0.05 mg/kg were achieved for 82% of the investigated pesticides.The applicability of this new approach for the screening of pesticides was finally proven by analyzing several commercial Atlantic salmon feed samples as well as various plant-based feed ingredients. Pirimiphos-methyl and ethoxyquin were among the most frequently detected analytes in the investigated samples.     

基于Hadoop的Kirchhoff叠前时间偏移并行算法

为了适应大规模地震勘探海量数据快速处理的需求,本文深入分析了地震勘探数据处理中广泛应用的Kirchhoff叠前时间偏移方法,提出了一种利用Hadoop技术实现叠前时间偏移的并行算法;采用数据的两次分块和内存循环利用等技术,提高了Kirchhoff叠前时间偏移海量数据处理效率。实际数据的测试表明,基于Hadoop的叠前时间偏移算法的计算效率比MPI版本提高了6.7%,同时在大规模生产应用条件下(大规模工区和大规模集群系统)具有更高的稳定性、容错性和适应性。