应用GC-MS/MS技术检测水果蔬菜中22种残留农药

目前,水果蔬菜生产中存在严重的滥施农药情况.水果蔬菜中常含有多种类型的残留农药,品种复杂多样.     

A Caputo–Fabrizio Fractional-Order Model of HIV/AIDS with a Treatment Compartment: Sensitivity Analysis and Optimal Control Strategies

Although most of the early research studies on fractional-order systems were based on the Caputo or Riemann–Liouville fractional-order derivatives, it has recently been proven that these methods have some drawbacks. For instance, kernels of these methods have a singularity that occurs at the endpoint of an interval of definition. Thus, to overcome this issue, several new definitions of fractional derivatives have been introduced. The Caputo–Fabrizio fractional order is one of these nonsingular definitions. This paper is concerned with the analyses and design of an optimal control strategy for a Caputo–Fabrizio fractional-order model of the HIV/AIDS epidemic. The Caputo–Fabrizio fractional-order model of HIV/AIDS is considered to prevent the singularity problem, which is a real concern in the modeling of real-world systems and phenomena. Firstly, in order to find out how the population of each compartment can be controlled, sensitivity analyses were conducted. Based on the sensitivity analyses, the most effective agents in disease transmission and prevalence were selected as control inputs. In this way, a modified Caputo–Fabrizio fractional-order model of the HIV/AIDS epidemic is proposed. By changing the contact rate of susceptible and infectious people, the atraumatic restorative treatment rate of the treated compartment individuals, and the sexual habits of susceptible people, optimal control was designed. Lastly, simulation results that demonstrate the appropriate performance of the Caputo–Fabrizio fractional-order model and proposed control scheme are illustrated.     

Facile and Scalable Synthesis of Si@void@C Embedded in Interconnected 3D Porous Carbon Architecture for High Performance Lithium-Ion Batteries

Si-based materials possess huge potential as an excellent anode material for Li-ion batteries. However, how to realize scalable synthesis of Si-based anode with a long cycling life and high-performance is still a critical challenge. Here a water-in-oil microemulsion process followed by UV illumination, calcination, and hydrothermal method to produce yolk-shell Si@void@C embedded in interconnected 3D porous carbon network architecture using silicon nanoparticles is reported. As a result, the sample Si@void@C/C-2 electrode has achieved a reversible capacity of 1160 mA h g⁻¹ at 0.2 A g⁻¹ after 300 cycles and a stable long cycling life of 480 mA h g⁻¹ at 1 A g⁻¹ after 1000 cycles. A full battery with the synthesized anode shows a capacity of 128 mA h g⁻¹ at 0.2 A g⁻¹ as well as good cycling stability after 1100th cycles. Such excellent electrochemical performance is ascribed to its unique structure, the yolk-shell void space, highly robust carbon shells and interconnected porous carbon nets that can improve the conductivity of the electrode, buffer the volume expansion, and also suppress Si nanoparticles stress variation. This water-in oil system makes it possible for mass production of environmentally friendly synthesis of core–shell structure.     

外部光注入的光泵浦自旋垂直腔表面发射激光器中的两个混沌偏振分量对两个复杂形状目标中的多区域精确测距

基于外部光注入的光泵浦自旋垂直腔表面发射激光器(vertical cavity surface-emitting laser,VCSEL)的两个混沌偏振分量,提出了对两个复杂形状目标中的多区域精确测距方案.这里,两个混沌偏振探测波具有飞秒量级快速动态并且被双极性sinc波形调制,使它们具有时空不相关特性.利用这些特性,通过计算多束延时反馈混沌偏振探测波形和与之相对应的参考波形的相关性,实现了对两个复杂形状目标多区域位置矢量精确测量.研究结果表明,对多区域小目标的测距具有非常低的相对误差(低于0.94%).当光电探测器的带宽足够大时,其测距的分辨率达到0.4 mm,并具有很强的抗噪声能力.本文的研究结果在复杂形状目标的精确测距方面具有潜在应用.     

基于双极性混沌序列的托普利兹块状感知矩阵

感知矩阵的构造是压缩感知从理论走向工程应用的关键技术之一.由于托普利兹感知矩阵能够支持快速算法且与离散卷积运算相对应,因此具有重要的研究意义.然而常用的随机托普利兹感知矩阵因其元素的不确定性,使得它在实际应用中受到了诸多约束,例如内存消耗较高和不易于硬件加载.基于此,本文结合双极性混沌序列的内在确定性和托普利兹矩阵的优点,提出了基于双极性混沌序列的托普利兹块状感知矩阵.具体地,首先介绍了双极性混沌序列的产生并分析了它的统计特性.其次,构造了双极性托普利兹块状混沌感知矩阵,从相关性方面证明了新建的感知矩阵具有近乎最优的理论保证,并同时证实了它满足约束等距条件.最后,研究了该感知矩阵针对一维信号和图像的压缩测量效果,并与典型感知矩阵进行了对比.结果表明,提出的感知矩阵对这些测试信号具有更好的测量效果,而且它在内存开销、计算复杂度和硬件实现等方面均具有明显的优势.特别地,该感知矩阵非常适用于多输入-单输出线性时不变系统的压缩感知测量问题.     

Synthesis,Structures, and Luminescent Properties of Lanthanide Complexes with Triphenylphospine Oxide

Seven lanthanide complexes [Ln(OPPh₃)₃(NO₃)₃] ( 1 – 3 ) (OPPh₃ = triphenylphosphine oxide, Ln = Nd, Sm, Gd), [Dy(OPPh₃)₄(NO₃)₂](NO₃) ( 4 ), [Ln(OPPh₃)₃(NO₃)₃]₂ ( 5 – 7 ) (Ln = Pr, Eu, Gd) were synthesized by the reactions of different lanthanide salts and OPPh₃ ligand in the air. These complexes were characterized by single‐crystal X‐ray diffraction analysis, elemental analysis, IR and fluorescence spectra. Structure analysis shows that complexes 1 – 4 are mononuclear complexes formed by OPPh₃ ligands and nitrates. The asymmetric units of complexes 5 – 7 consist of two crystallographic‐separate molecules. Complex 1 is self‐assembled to construct a 2D layer‐structure of (4,4) net topology by hydrogen bond interactions. The other complexes show a 1D chain‐like structure that was assembled by OPPh₃ ligands and nitrate ions through C–H ··· O interactions. Solid emission spectra of compounds 4 and 6 are assigned to the characteristic fluorescence of Tb³⁺ (λ_em = 480, 574 nm) and Eu³⁺ (λ_em = 552, 593, 619, 668 nm).     

Direct cross-coupling of aryl alkynyliodines with arylsulfinic acids leading to alkynyl sulfones under catalyst-free conditions

A facile and efficient one-pot method has been developed for the construction of alkynyl sulfones via direct cross-coupling reaction of aryl alkynyliodines and arylsulfinic acids. The present transformation could be accomplished under catalyst- and additive-free conditions, providing a series of alkynyl sulfones in moderate to good yields with favorable functional group tolerance.     

Novel phosphorescent neutral iridium(III) complex with the steric hindrance for highly efficient red organic light-emitting diodes

A novel and highly efficient thiophenquinolone-based red iridium(III) complex bearing a bulky fluorophenyl moiety is designed and synthesized. The complex shows intensive red phosphorescence (596 nm with shoulder at 642 nm), high photoluminescence efficiency (0.62) and broad full width at half maximum (81 nm). The bulky fluorophenyl moiety introduced into the complex could improve the efficiency of electroluminescence with the maximum current efficiency, power efficiency and the external quantum efficiency up to 29.0 cd/A, 30.4 lm/W and 17.6% due to the effective steric hindrance in solid states.     

Ultrasensitive amperometric determination of PSA based on a signal amplification strategy using nanoflowers composed of single-strand DNA modified fullerene and Methylene Blue,and an improved surface-initiated enzymatic polymerization

The authors describe a signal amplification strategy for highly sensitive detection of the prostate-specific antigen (PSA). This is accomplished by a combination of two methods, viz. (a) improved surface-initiated enzymatic polymerization (SIEP), and (b) the use of nanoflowers prepared from C₆₀ fullerene and Methylene Blue (C₆₀/MB) modified with a long single-strand DNA. C₆₀/MB acts as a novel electrochemical indicator. The C₆₀/MB nanoflowers improve the load of MB and promote the electron transfer. The integration of the SIEP technique and the C₆₀/MB nanomaterial also results in improved loading of MB on the nucleic acid. Ultimately, dual cascade signal amplification is accomplished. The biosensor was constructed as follows: (a) Gold nanospheres were modified with antibody 2 (Ab₂) and a thiolated oligonucleotide (referred to as S₀). (2) S₀ is then extended by the SIEP reaction. (3) The redox indicator C₆₀/MB is then connected to the extended guanine-rich ssDNA which then yields the amperometric signal. (4) A sandwich immunoassay is performed by capturing the nanoprobe oy type Ab₂-Au-S₀ on the gold electrode modified with multi-walled carbon nanotubes (MWCNTs) and protein A. Current is measured by using differential pulse voltammetry (DPV). The synergic effect of the biofunctional nanomaterial and the signal amplification strategy greatly improves the performance of this immunoassay. Under optimized conditions and at a working voltage of typically ?0.18 V (vs Ag/AgCl), the assay has a linear range that extends from 15 pg·mL^?1 to 8 ng·mL^?1 of PSA. The detection limit is as low as 1.7 pg·mL^?1 (at an S/N ratio of 3). In our perception, this dual amplification scheme has a wide scope in that it may become applicable to numerous other immunoassays.

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Graphical abstract C₆₀/Methylene blue nanoflowers, a novel electrochemical indicator, connect with the long single-stranded DNA (ssDNA) extended by the improved surface-initiated enzymatic polymerization method. This amplification strategy is utilized to construct a sandwich prostate-specific antigen (PSA) immunosensor.