Synthesis, spectroscopic characterization, and antimicrobial activity of cobalt(II) complexes of acetone-N(4)-phenylsemicarbazone: crystal structure of [Co(HL)2(MeOH)2](NO3)2

Four Co(II) complexes, [Co(HL)₂](OAc)₂, [Co(HL)₂Cl₂], [Co(HL)₂(MeOH)₂](NO₃)₂, and [Co₂(HL)₄(SO₄)₂] (HL = acetone-N(4)-phenylsemicarbazone) were synthesized and characterized by physicochemical and spectroscopic methods. The magnetic susceptibility measurements indicate that the complexes are paramagnetic with three unpaired electrons. In all the complexes, the semicarbazone is coordinated as a neutral bidentate ligand. The structure of [Co(HL)₂(MeOH)₂](NO₃)₂ was confirmed by single crystal X-ray crystallography. The ligand is neutral and bidentate, being coordinated to the cobalt atom through the carbonyl oxygen and the azomethine nitrogen. Intermolecular hydrogen bonding and C–H···π interactions combine to stabilize the crystal structure. The ligand and its two complexes [Co(HL)₂Cl₂] and [Co(HL)₂(MeOH)₂](NO₃)₂ were screened for their antibacterial and antifungal activities using disk diffusion methods.     

Synthesis and bioactivity of novel coumarin derivatives containing(E)-methyl 2-(methoxyimino)-2-phenylacetates

Ten coumarin derivatives containing(E)-methyl 2-(methoxyimino)-2-phenylacetate were synthesized and bioassayed.The compounds were identified by IR,~1H NMR and elemental analyses.The test results indicated that compound 5j(R~1 is methyl and R~2 is n-C_6H_(13)) was the optimal structure in this paper with good fungicidal activity against CDM(85%) at 6.25 mg/L concentration.     

Simultaneous determination of three 5-nitroimidazoles in foodstuffs by differential pulse voltammetry and chemometrics

The voltammetric behaviour of three 5-nitroimidazoles,metronidazole,tinidazole and ornidazole,was investigated,and a method was developed for the simultaneous determination of these compounds,based on their reduction at a hanging mercury drop electrode(HMDE) in pH 8.95 buffer with differential pulse voltammetric(DPV) approach.Well defined voltammetric waves with peak potentials of -692,-640 and -652 mV were observed for these compounds,respectively.It is difficult to determine them individually from their mixtures without preseparation,for their voltammetric peaks overlapped seriously,so the chemometrics were used to resolve the overlapped voltammogram and quantify the mixtures.The proposed method was successfully applied to the determination of three 5-nitroimidazoles in milk and honey samples.     

卷积算子的Gibbs现象

本文建立了一般卷积算子在函数的第一类间断点处有Gibbs现象的刻画定理,并且给出了某些例子.     

Thermodynamics and selectivity of two-dimensional metallo-supramolecular self-assembly resolved at molecular scale

We investigated the thermodynamic processes of two-dimensional (2D) metallo-supramolecular self-assembly at molecular resolution using scanning tunneling microscopy and variable-temperature low-energy electron diffraction. On a Au(111) substrate, tripyridyl ligands coordinated with Cu in a twofold Cu-pyridyl binding mode or with Fe in a threefold Fe-pyridyl binding mode, forming a 2D open network structure in each case. The network structures exhibited remarkable thermal stability (600 K for the Cu-coordinated network and 680 K for the Fe-coordinated network). The Fe-pyridyl binding was selected thermodynamically as well as kinetically in self-assembly involving both modes. The selectivity can be effectively suppressed in a specifically designed self-assembly route.     

Simultaneous Determination of Cimaterol, Salbutamol, Terbutaline and Ractopamine in Feed by SPE Coupled to UPLC

An ultra performance liquid chromatography (UPLC) method was established for the simultaneous determination of cimaterol, salbutamol, terbutaline, and ractopamine in feed. Target compounds were extracted with methanol and centrifuged. The supernatant was then transferred and concentrated, and applied to a solid phase extraction MCX cartridge for clean-up before UPLC analysis. The calibration curves for the four ??-agonists were good linear in concentration range of 0.05?C1.0 ??g mL^?1 with the correlation coefficients (r) over 0.999. The average recoveries were in the range of 90.1?C101.4% with relative standard deviation values lower than 8.0%.     

Selective supramolecular assembly of multifunctional ligands on a Cu(111) surface: metallacycles, propeller trimers and linear chains

We studied the supramolecular assembly of a multifunctional ligand, cis-bis-terpyridine tetraphenyl ethylene, on a Cu(111) surface by low-temperature scanning tunneling microscopy (STM). Three distinctive supramolecular structures, metallacycles, propeller-shaped clusters and extended linear chains, are formed under specific assembly conditions owing to different inter-molecular binding modes of Cu-coordination, van der Waals interaction and hydrogen bonding, respectively.     

A reversible fluorescence nanoswitch based on bifunctional reduced graphene oxide: use for detection of Hg2+ and molecular logic gate operation

Herein, we demonstrate the first use of a reduced graphene oxide (rGO)-organic dye nanoswitch for the label-free, sensitive and selective detection of Hg(2+) using bifunctional rGO as an effective nanoquencher and highly selective nanosorbent. Moreover, a reversible on-off INHIBIT rGO logic gate based on a cysteine-Hg(2+) system has also been designed.     

Optimal uncertainty size in distributionally robust inverse covariance estimation

In a recent paper, Nguyen et al. (2018) built a distributionally robust estimator for the precision matrix of the Gaussian distribution. The distributional uncertainty size is a key ingredient in the construction of this estimator. We develop a statistical theory which shows how to optimally choose the uncertainty size to minimize the associated Stein loss. Surprisingly, rather than the expected canonical square-root scaling rate, the optimal uncertainty size scales linearly with the sample size.     

二维核磁共振数据的噪声剔除与数据压缩

讨论了对二维核磁共振数据进行噪声剔除与数据压缩的一般原理与方法,介绍在Sun图形工作站上的实现情况,并给出实验结果与分析。