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901.
Huizhong Sun Pu Wang Honghua Li Yingming Li Shucheng Zheng Julius Matsiko Yanfen Hao Weiwei Zhang Dou Wang Qinghua Zhang 《中国科学:化学(英文版)》2017,60(5):670-677
A method was developed on a gas chromatograph coupled to a triple quadrupole mass spectrometer(GC-MS/MS) for trace level determination of polychlorinated dibenzo-p-dioxins/dibenzofurans(PCDD/Fs) and dioxin-like polychlorinated biphenyls(DL-PCBs) in food and feed. The results demonstrated good sensitivity and repeatability for PCDD/Fs and DL-PCBs at an extremely low level(10 pg mL~(-1) for 2,3,7,8-TCDD/F), as well as wide linear response of over 3 or 4 orders of magnitude in concentration ranges; 0.5–200 ng mL~(-1) for PeCDD/F and 0.2–2000 ng mL~(-1) for DL-PCBs. The method detection limits for PCDD/Fs and DL-PCBs were in the range from 0.018–0.17 pg g~(-1) to 0.13–0.36 pg g~(-1), respectively. The performance of the GC-MS/MS for food and feed sample analysis showed high precision and accuracy compared to the high resolution gas chromatograph/high resolution mass spectrometer. The results indicated the feasibility of GC-MS/MS as a confirmatory method for the measurement of PCDD/Fs and DL-PCBs in food and feed as required by European Union legislation. 相似文献
902.
In this paper, the Euler–Maruyama (EM) method with random variable stepsize is studied to reproduce the almost sure stability of the true solutions of stochastic differential equations. Since the choice of the time step is based on the current state of the solution, the time variable is proved to be a stopping time. Then the semimartingale convergence theory is employed to obtain the almost sure stability of the random variable stepsize EM solution. To our best knowledge, this is the first paper to apply the random variable stepsize (with clear proof of the stopping time) to the analysis of the almost sure stability of the EM method. 相似文献
903.
Pu?Zhang Yi?WangEmail authorView authors OrcID profile Ling?Chen Yibing?Yin 《Mikrochimica acta》2017,184(10):3781-3787
Gold-silver nanoclusters (Au-AgNCs) were synthesized by simultaneous chemical reduction of Au(III) and Ag(I) ions in one pot, using bovine serum albumin as both a template and a reductant. The Au-AgNCs have an average size of 2.4 nm and display strong red fluorescence (with an emission peak at 610 nm on excitation at 360 nm). The fluorescence quantum yield can reach 18.6%. Fluorescence is strongly quenched by hypochlorite, while other common anions have minor (or no) effects on fluorescence. Based on these findings, a fluorometric method was developed for the determination of hypochlorite. The method has a linear response in the 0.7 to 15 μM concentration range, with a limit of detection as low as 80 nM. It was successfully applied to the determination of hypochlorite in (spiked) tap water. 相似文献
904.
We show that a robust macroscopic atom-molecule dark state can exist in fermionic systems, which represents a coherent superposition between the ground molecular Bose-Einstein condensates and the atomic BCS paired state. We take advantage of the tunability offered by external laser fields, and explore this superposition for demonstrating coherent oscillations between ground molecules and atom pairs. We interpret the oscillation frequencies in terms of the collective excitations of the dark state. 相似文献
905.
Teruo Beppu Kosuke Tomiguchi Akito Masuhara Yong‐Jin Pu Hiroshi Katagiri 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(25):7440-7443
Benzene is the simplest aromatic hydrocarbon with a six‐membered ring. It is one of the most basic structural units for the construction of π conjugated systems, which are widely used as fluorescent dyes and other luminescent materials for imaging applications and displays because of their enhanced spectroscopic signal. Presented herein is 2,5‐bis(methylsulfonyl)‐1,4‐diaminobenzene as a novel architecture for green fluorophores, established based on an effective push–pull system supported by intramolecular hydrogen bonding. This compound demonstrates high fluorescence emission and photostability and is solid‐state emissive, water‐soluble, and solvent‐ and pH‐independent with quantum yields of Φ=0.67 and Stokes shift of 140 nm (in water). This architecture is a significant departure from conventional extended π‐conjugated systems based on a flat and rigid molecular design and provides a minimum requirement for green fluorophores comprising a single benzene ring. 相似文献
906.
Three new asymmetrical diarylethenes containing an azaindole moiety and a variable heteroaryl ring have been synthesized. Their properties, such as photochromism, fatigue resistance, thermal stability, acidichromism, and fluorescence, were systematically investigated to elucidate the effects of aromatic stabilization energies (ASE) of the heteroaryl moieties. The results indicated that thermal stability decreased with the increment of the aromatic stabilization energies of the variable heteroaryl rings in the order of thiazyl<thienyl<pyrrolyl. Moreover, the dual switching behaviors of these azaindole‐containing diarylethenes were also studied by the stimulation of acid/base and light. Addition of trifluoroacetic acid to the solutions of these diarylethenes resulted in obvious hypochromic shifts, and their N‐protonated forms also exhibited favorable photochromism. 相似文献
907.
A novel and facile synthesis of 4-arylquinolin-2(1H)-ones without metal catalysis has been developed. This reaction involved cyclization/elimination steps and was performed under metal-free conditions using inexpensive reagents such as NaI, selectfluor and KOH. 相似文献
908.
A new secondary metabolite, 2-O-methylalternariol 4-O-β-[4-methoxyl-glucopyranoside] (1), together with four known compounds alternariol methyl ether (2), altenuene (3), isoaltenuene (4) and 2-(2′S-hydroxypropyl)-5-methyl-7-hydroxychromone (5), was isolated from the fungus Alternaria alternate cib-137. Its structure was elucidated on the basis of spectroscopic data. Compounds 3 and 4 demonstrated moderate activity against Staphylococcus aureus. 相似文献
909.
Guanghao Wu Prof. Jinfeng Zhang Qianru Zhao Wanru Zhuang Jingjing Ding Chi Zhang Haijun Gao Dai-Wen Pang Prof. Kanyi Pu Prof. Hai-Yan Xie 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(10):4097-4103
Atherosclerosis (AS) is a major contributor to cardiovascular diseases worldwide, and alleviating inflammation is a promising strategy for AS treatment. Here, we report molecularly engineered M2 macrophage-derived exosomes (M2 Exo) with inflammation-tropism and anti-inflammatory capabilities for AS imaging and therapy. M2 Exo are derived from M2 macrophages and further electroporated with FDA-approved hexyl 5-aminolevulinate hydrochloride (HAL). After systematic administration, the engineered M2 Exo exhibit excellent inflammation-tropism and anti-inflammation effects via the surface-bonded chemokine receptors and the anti-inflammatory cytokines released from the anti-inflammatory M2 macrophages. Moreover, the encapsulated HAL can undergo intrinsic biosynthesis and metabolism of heme to generate anti-inflammatory carbon monoxide and bilirubin, which further enhance the anti-inflammation effects and finally alleviate AS. Meanwhile, the intermediate protoporphyrin IX (PpIX) of the heme biosynthesis pathway permits the fluorescence imaging and tracking of AS. 相似文献
910.
This paper is concerned with the stabilization problem of uncertain chaotic systems with input nonlinearity. The slope parameters of this nonlinearity are unmeasured. A new sliding function is designed, then an adaptive sliding mode controller is established such that the trajectory of the system converges to the sliding surface in a finite time and finite-time reachability is theoretically proved. Using a virtual state feedback control technique, sufficient condition for the asymptotic stability of sliding mode dynamics is derived via linear matrix inequality (LMI). Then the results can be extended to uncertain chaotic systems with disturbances and adaptive sliding mode H ∞ controllers are designed. Finally, a simulation example is presented to show the validity and advantage of the proposed method. 相似文献