Eco friendly synthesis of fluorescent carbon dots for the sensitive detection of ferric ions and cell imaging

This study established a ferric ion (Fe³⁺) detection method as a result of the fluorescence quenching effect of Fe³⁺ on carbon dots (CDs). Specifically, we proposed, a green microwave synthesis route towards fluorescent CDs that requires only the brewer’s spent grain as starting materials. Transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectra and X-ray photoelectron spectroscopy were performed to investigate the CDs characteristic: morphology, size distribution, functional groups, and composition, respectively. The experimental results, which were run under optimal experimental conditions, indicated that the fluorescence intensity and concentration of Fe³⁺ were within the desired linear range (0.3–7 μM). The detection limit of this assay towards Fe³⁺ was 95 nM. The proposed method showed significant selectivity with respect to interfering ions. We evaluated the potential application of this method with tap water, lake water and fetal bovine serum as real samples. Additionally, the CDs could be served as superior bioimaging probes in Hela cells as a result of their excellent optical stability and good biocompatibility. In a word, the present study provides a new idea for CDs derived from the waste of agricultural products for detecting food or environmental contaminants and cell imaging.     

基于虚拟仪器的换热器智能控制系统设计

换热器广泛应用于建筑工程领域及工业过程中,其出口介质温度的有效控制是保证质量、节能和安全生产的重要条件,因此换热器出口水温的控制是过程控制中的重要课题。本文以西门子SMPT1000换热器温度控制系统为研究对象,建立基于虚拟仪器的智能温度控制平台。该平台在实现传统PID控制的基础上,又增加了智能控制算法,斯密斯控制和模糊控制。实验证明该智能控制平台具有修改参数简易方便、曲线准确的优点,具有良好的动静态特性,且市场应用价值高。     

Surface characteristics and electrochemical behaviour of sputter-deposited NiTi thin film

Thin nanocrystalline amorphous NiTi film was deposited on Si substrate using DC magnetron sputtering. The as-deposited NiTi thin film was crystallized by heat treatment at 500 °C for 1 h. The crystal structure, surface morphology, microstructure and surface chemistry of the deposited films were studied using X-ray diffraction, atomic force microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy (XPS), respectively. Corrosion behaviour was assessed in Ringer’s solution at 37 °C by open circuit potential (OCP), potentiodynamic polarization and electrochemical impedance spectroscopy as a function of exposure time. OCP values indicate that the tendency for the formation of a spontaneous oxide film is greater for the NiTi thin films than the bulk NiTi. Long time exposure to Ringer’s solution was found to have a great effect on the corrosion behaviour of the samples. Significantly low corrosion current density was obtained for the annealed NiTi film from the potentiodynamic polarization curves indicating a typical passive behaviour, but as-deposited film and bulk NiTi alloy exhibited breakdown of passivity at potentials approximately +1.4 V (vs. SCE). XPS showed that the oxide film formed on the annealed NiTi thin film mainly composed of Ti oxides, and no evidence of Ni was found up to 8.2 nm beneath the top surface, suggesting the excellent corrosion resistance of this sample in Ringer’s solution.     

用于荧光光谱测定的微量固体粉末样品制样优化*

为满足微量固体粉末荧光检测要求,采用薄层制样法,改变黏结剂种类、黏结剂的用量、涂层厚度以及后处理方法来进行其制样工艺优化。 结果表明:以聚乙烯醇做黏结剂、1∶5的固液比、在50 ℃烘干30 min、涂片次数3层的薄层制样优化工艺可满足荧光固体测样的要求。采用t检验比较固体样品池装样和薄层制样法的荧光检测结果发现两者无显著性差异,薄层制样优化工艺的需样量较样品池减少90%。     

β-secretase 1 inhibitory activity and AMP-activated protein kinase activation of Callyspongia samarensis extracts

Abstract

The methanolic extract of Callyspongia samarensis (MCS) significantly inhibited β-secretase 1 (IC₅₀ 99.82?µg/mL) in a dose-dependent manner and demonstrated a noncompetitive type of inhibition. Furthermore, it exhibited the highest AMPK activation (EC₅₀ 14.47?μg/mL) as compared with the standard, Aspirin (EC₅₀ >100?μg/mL). HPLC/ESI-MS analysis of MCS extract revealed 15 peaks, in which nine peaks demonstrated similar fragmentation pattern with the known compounds in literature and in database library: 5-aminopentanoic acid (1), 4-aminobutanoic acid (3), Luotonin A (4), (E)-3-(1H-imidazol-5-yl) prop-2-enoic acid (8), Galactosphingosine (10), D-sphingosine (11), 5,7,4′-trihydroxy-3′,5′-dimethoxyflavone (12), hydroxydihydrovolide (13), and 3,5-dibromo-4-methoxyphenylpyruvic acid (14); and 6 peaks are not identified (2, 5–7, 9, and 15). Acute oral toxicity test of MCS extract revealed that it is nontoxic, with an LD₅₀ of >2000?mg/kg. Assessment of BBB permeability of MCS extract showed that compound 15 was able to cross the BBB making it a suitable candidate for developing CNS drugs.     

Toonapolyynes A–D,new polyynes from Toona ciliata

Abstract

Phytochemical investigation on the leaves and twigs of Toona ciliata has led to the isolation of four new polyynes (1–4) and two knowns (5 and 6). Their structures were determined by extensive spectroscopic analysis (MS, UV, IR, and NMR) and Mosher’s method. All compounds were evaluated for their inhibitory activities against HepG2 human tumor cell line but were inactive.     

Herbarumin Ⅲ的立体选择性全合成

以正丁醛和1,5-戊二醇为起始原料, 以不对称烯丙基化、改良的Julia成烯反应和Yamaguchi内酯化为关键步骤, 通过13步反应, 立体选择性地合成了具有植物毒性的天然十元内酯化合物Herbarumin Ⅲ(3)及其差向异构体22.     

Sobolev-Lorentz范数约束下的次临界型Adams不等式

本文在Sobolev-Lorentz空间W2L2,q(R4)的范数约束下得到了一个最佳的二阶次临界型Adams不等式.进一步,当次临界指标逼近最佳常数时,得到了Adams泛函的上、下界的估计.本文主要采用了Lam和Lu[A new approach to sharp Moser-Trudinger and Adams ...     

Acoustoelastic effect simulation by time–space finite element formulation based on quadratic interpolation of the acceleration

Acoustoelastic effect describes the change of ultrasound velocity due to the initial stress. Its simulation involves a numerical analysis of nonlinear elastodynamics and requires high accuracy in the time domain. A time–space finite element formulation, derived from the quadratic interpolation of the acceleration within a time segment, is proposed for an accurate simulation of the acoustoelastic effect in the present study. Ten different integration schemes are generated based on this formulation and nine of them are found to be conditionally stable. Among the nine stable schemes, one is found to obtain a spectral radius of one when the normalized step ratio is less than 5.477, indicating no numerical dissipation or numerical divergence. Compared with integration schemes from previous studies, this integration scheme demonstrates better performance in calculation accuracy and energy conservation. A two-stage approach, namely the static stage and the dynamic stage, has been employed in the simulation of the acoustoelastic effect. The former stage is adopted to obtain the initial stress and the latter stage, where the proposed integration scheme is implemented, is adopted to simulate the ultrasound propagation in an initial stress state. The simulation results of the dynamic stage show that the ultrasound velocity increases in a compression stress state and decreases in a tension stress state for aluminum alloy, which is in good agreement with previous experimental studies. Together with the simulation result of the static stage, it is conjectured that the acoustoelastic effect results from the stress-dependent elastic modulus.