Residue analysis of tebufenozide and indoxacarb in chicken muscle,milk, egg and aquatic animal products using liquid chromatography–tandem mass spectrometry

We developed an analytical method using liquid–liquid extraction (LLE) and liquid chromatography–tandem mass spectrometry (LC‐MS/MS) to detect and quantify tebufenozide (TEB) and indoxacarb (IND) residues in animal and aquatic products (chicken muscle, milk, egg, eel, flatfish, and shrimp). The target compounds were extracted using 1% acetic acid (0.1% acetic acid for egg only) in acetonitrile and purified using n‐hexane. The analytes were separated on a Gemini‐NX C₁₈ column using (a) distilled water with 0.1% formic acid and 5 mm ammonium acetate and (b) methanol with 0.1% formic acid as the mobile phase. All six‐point matrix‐matched calibration curves showed good linearity with coefficients of determination (R²) ≥0.9864 over a concentration range of 5–50 μg/kg. Intra‐ and inter‐day accuracy was expressed as the recovery rate at three spiking levels and ranged between 73.22 and 114.93% in all matrices, with a relative standard deviation (RSD, corresponding to precision) ≤13.87%. The limits of quantification (LOQ) of all target analytes ranged from 2 to 20 μg/kg, which were substantially lower than the maximum residue limits (MRLs) specified by the regulatory agencies of different countries. All samples were collected from different markets in Seoul, Republic of Korea, and tested negative for tebufenozide and indoxacarb residues. These results show that the method developed is robust and may be a promising tool to detect trace levels of the target analytes in animal products.     

Bimetallic oxide nanoparticles confined in ZIF‐67‐derived carbon for highly selective oxidation of saturated C–H bond in alkyl arenes

Zeolite imidazolate frameworks (ZIFs) have recently emerged as an ideal type of carbon precursors with abundant tailorability. In this work, a series of ZIF‐derived porous carbon catalysts have been prepared with encapsulation of bimetallic oxide nanoparticles via simple thermal treatment. The composition and structure of these catalysts were confirmed in detail by different characterization methods. The bimetallic oxide (Mn/Co, Fe/Co, and Cu/Co) nanoparticles were encapsulated in the nitrogen‐doped graphitized carbon matrix. Moreover, the hierarchically porous structure and carbon defects were successfully constructed in the carbon catalysts. Additionally, in the selective oxidation of saturated C–H bonds in alkyl arenes, the carbon catalysts demonstrate outstanding performance for the oxidation of C–H bonds to corresponding carboxyl groups. This was due to their unique structure can greatly promote mass transfer and molecular oxygen activation, resulting in high conversion and high selectivity. Remarkably, this work here could also provide a novel strategy to the controllable synthesis of metal–organic frameworks (MOFs)‐derived carbon catalysts for enhanced performance in heterogeneous catalysis.     

点集拓扑学之杨忠道定理的一个机械化证明

本文给出一种用高阶逻辑自动证明语言Isabelle在计算机中表示拓扑空间中开集、闭集、邻域和导集等基本概念的方法,在此基础上证明点集拓扑学中著名的杨忠道定理,即一拓扑空间的任意单点集的导集为闭集,则其任意子集的导集亦为闭集.     

Cu(I) camphor coordination polymers: Synthesis and study of the catalytic activity for cyclization of 4‐pentyn‐1‐oic acid

The number of CuCl units per camphor ligand in [{CuCl}₂L]_n was extended to three or four in [{CuCl}₃L]_n ( 2 ) or [{CuCl}₄L]_n ( 1 ). The Hartree‐Fock ab initio calculations support the polymeric structure of 1 and 2 that catalyze the cyclization of 4‐pentyn‐1‐oic acid ( A ) forming 5‐methylenedihydrofuran‐2(3H)‐one ( B ) and/or 2‐methyl‐5‐oxotetrahydrofuran‐2‐ylpent‐4‐ynoate ( C ). The catalytic activity of 1 , 2 and other polynuclear Cu(I) complexes ( 3–5 ) was evaluated under solvent free conditions and/or solution. In the absence of solvent, catalyst 2 displays the highest activity and selectivity (75.8/23.1, C to B ratio, at 5.4% loading) while 4 reaches the highest level of A → B conversion (97.5 %) in solution. Selected reactions were followed by NMR and the kinetic constants calculated. A mechanism is proposed based on the equations used for the calculations. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3316–3323     

Koszul differential graded modules

The concept of Koszulity for differential graded (DG, for short) modules is introduced. It is shown that any bounded below DG module with bounded Ext-group to the trivial module over a Koszul DG algebra has a Koszul DG submodule (up to a shift and truncation), moreover such a DG module can be approximated by Koszul DG modules (Theorem 3.6). Let A be a Koszul DG algebra, and Dc(A) be the full triangulated subcategory of the derived category of DG A-modules generated by the object AA. If the trivial DG module...     

Electric field-derived point charges to mimic the electrostatics in molecular crystals

Because of the way the electrostatic potential is defined in a crystal, it is not possible to determine potential-derived charges for atoms in a crystal. To overcome this limitation, we present a novel method for determining atomic charges for a molecule in a crystal based on a fit to the electric field at points on a surface around the molecule. Examples of fits to the electric field at points on a Hirshfeld surface, using crystal Hartree-Fock electron densities computed with a DZP basis set are presented for several organic molecular crystals. The field-derived charges for common functional groups are transferable, and reflect chemical functionality as well as the subtle effects of intermolecular interactions. The charges also yield an excellent approximation to the electric field surrounding a molecule in a crystal for use in cluster calculations on molecules in solids.     

Influence of noise and delay on reaction-diffusion recurrent neural networks

In this paper, the influence of the noise and delay upon the stability property of reaction-diffusion recurrent neural networks （RNNs） with the time-varying delay is discussed. The new and easily verifiable conditions to guarantee the mean value exponential stability of an equilibrium solution are derived. The rate of exponential convergence can be estimated by means of a simple computation based on these criteria.     

整代数体函数与其导函数的增长级

对整代数体函数与其导函数的增长性进行了研究,得到了整代数体函数与其导函数的特征函数之间关系式,并证明了它们具有相同的级和下级,从而将亚纯函数的相应结果推广到了整代数体函数.     

The derived category of an algebra with radical square zero

Koszul duality and covering theory are combined to realize the bounded derived category 𝒟 of an algebra with radical square zero as a certain orbit category of the bounded derived category of finitely presented representations of an associated infinite quiver. As a consequence, the possible shapes of the connected components of the Auslander–Reiten quiver of 𝒟 are described.     

Degradation of Polyolefins Prepared with Fischer-Tropsch Derived Olefins

Degradation of some copolymers of ethylene with Fischer-Tropsch derived olefins was investigated. Hydroperoxide and carbonyl formation in samples of ethylene copolymers with heptene-1, and ethylene multiple polymers with the Fischer-Tropsch derived 3,4 methyl-pentene and linear olefins were monitored by IR spectroscopy. The results correlated with results obtained from thermogravimetry, multiple extrusion and rheology in previous studies. It was shown that degradation of ethylene with Fischer-Tropsch derived olefins is related to the type of branch introduced into the chain by the copolymerization with the particular olefin.