Phthalates represent a potential risk for humans, since they are ubiquitous environmental contaminants. Efficient extraction and purification procedures are demanded for the detection of low concentration levels of phthalates. In this work, a novel type of molecularly imprinted polymers coated onto the surface of vinyl functionalized multi-walled carbon nanotubes was synthesized and coupled with gas chromatography–mass spectrometry (GC/MS) for the selective separation and determination of dioctyl phthalate (DOP) in beverage samples. The morphology, structure property, and thermostability of the resultant polymers were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The adsorption properties of the prepared polymers were investigated by equilibrium rebinding and competitive experiments. The resultant imprinted nanomaterials exhibited high capacity and favorable selectivity. In addition, the feasibility of the developed method using the obtained imprinted polymers as a solid-phase sorbent coupled with GC/MS for the selective isolation and determination of DOP in different beverage samples was demonstrated. Under optimal conditions, the limit of detection of the proposed method for DOP was 2.3 ng L−1. DOP spiked at three levels of concentration in beverage samples was extracted and determined through the application of the present method, with recoveries ranging from 88.6 to 93.0 % with relative standard deviations less than 5.6 %.

Molecularly imprinted polymers for dimethoate recognition were synthesized by the precipitation polymerization technique using methyl methacrylate(MMA) as the functional monomer and ethylene glycol dimethacrylate(EGDMA) as the cross-linker.The morphology,adsorption and recognition properties were investigated by scanning electron microscopy(SEM),static adsorption test,and competitive adsorption test.To obtain the best selectivity and binding performance,the synthesis and adsorption conditions of MIPs were optimized through single factor experiments.Under the optimized conditions,the resultant polymers exhibited uniform size,satisfactory binding capacity and significant selectivity.Furthermore,the imprinted polymers were successfully applied as a specific solid-phase extractants combined with high performance liquid chromatography(HPLC) for determination of dimethoate residues in the cucumber samples.The average recoveries of three spiked samples ranged from 78.5% to 87.9% with the relative standard deviations(RSDs) less than 4.4% and the limit of detection(LOD) obtained for dimethoate as low as 2.3 μg/mL.

An efficient method is provided to detect simultaneously some important veterinary drugs from different classes in highly complex animal tissue matrix. This method using matrix solid-phase dispersion (MSPD) and high performance liquid chromatography (HPLC) with diode array detection (DAD) is developed to effectively determine two fluoroquinolones (enoxacin and lomefloxacin), two sulfonamides (sulfanilamide and sulfamethoxazole) and one tetracycline (tetracycline) simultaneously in porcine tissues. In the process, MSPD methodology was used to treat samples, washed by n-hexane to remove lipid, eluted the analytes with acetonitrile–dichloromethane (1:1, v/v). Solvent acetonitrile and solvent acetic acid (0.1%) were combined in a gradient. HPLC–DAD analysis of the tissue samples was performed within 15min at a flow rate of 1.0mL/min. The results showed that a recovery at 0.1, 0.5 and 1.0μg/g fortification levels ranged from 80.6% to 99.2% with satisfactory relative standard deviations (RSDs) (below 6.1%, n=3) and the limits of quantitation (LOQ) ranged from 7μg/kg to 34μg/kg in porcine tissues. Utilization of the method in successfully simultaneous analysis of porcine tissue incurred with veterinary drug multiresidues is described.

A rapid method has been developed based on the sample preparation procedure named as QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe), combined with reversed-phase high performance liquid chromatography with fluorescence detector and C18 column after pre-column derivatization using o-phthalaldehyde and 2-mercaptoethanol to determine dopamine in porcine muscle. Methanol and deionized water (0.1% acetic acid, v/v) with a ratio of 60:40 was used as mobile phase. The flow rate was 0.8 mL/min and dopamine was eluted within 15 min. The linearity range was 0.003-8 μg/mL with r=0.9992. The detection limit for dopamine was 4 μg/kg and the quantification limit was 9 μg/kg. Recovery studies were carried out at 0.1, 0.5 and 1.0 mg/kg fortification levels and the average recoveries obtained ranged from 90.4% to 98.2% with relative standard deviations between 3.5% and 8.1%. The method was found to be suitable for detection of dopamine in animal product tissues at the maximum residue level.

Increasing concerns on public health safety have led researchers to develop efficient methods to characterize veterinary drugs and pesticides residues simultaneously in animal products. This investigation presents a simple and rapid method to determine five types of fluoroquinolones (FQs), organophosphorus (OP) and N-methyl carbamates (NMCs) in porcine tissue simultaneously with the use of matrix solid-phase dispersion (MSPD), high performance liquid chromatography (HPLC) and diode array detection (DAD). The results show a recovery ratio of 60.1–107.7% with satisfactory relative standard deviations. The limits of detection (LOD) in porcine tissue are between 9 and 22μg/kg. The applicability of the method to the multiresidue analysis in porcine tissue is reported in this contribution.

A practical, inexpensive, and green chemical process is greatly needed for degrading pesticides in food and environmental water. In this work, the impact of O(2) plasma treatment on reduction of dichlorvos (DDVP) and omethoate in maize was determined by gas chromatography (GC). The main plasma-induced degradation mechanisms were investigated through identification of intermediates or products during O(2) plasma treatment for DDVP and omethoate on solid surfaces by gas chromatography/mass spectrometry (GC/MS). The results clearly demonstrate that O(2) plasma treatment is significantly effective in the degradation of original DDVP and omethoate, and the degradation efficiency mainly depends upon related operating parameters and chemical structures of pesticides. Moreover, GC/MS analyses show that DDVP and omethoate molecules are degraded into less-toxic compounds, and the plasma degradation mechanisms for pesticides can be dominated by a free-radical reaction. It is concluded that O(2) plasma has the potential to reduce pesticide residues in agricultural products.

Antioxidant and estrogenic effects of formononetin on ovariectomized mice have been investigated in the present study. The adult female Kunming mice were divided into 5 groups: sham-operated group, ovariectomized group, stilbestrol replacement therapy group (0.20 mg/kg day), low-dose formononetin group (0.05 g/kg day) and high-dose formononetin group (0.5 g/kg day). The mice in the latter 4 groups were ovariectomized. The drug was given by oral administration for 6 months. Estrogenic effect was determined by the change of uterine weight, and oxidant effects were determined by the content of SOD, GSH-Px, CAT and MDA. The intake of formononetin increased the uterine weight of the mice significantly as well as the content of SOD, GSH-Px, CAT, and reduced MDA in body. Formononetin had obvious antioxidant effects and estrogenic effect, and the estrogenic effect was not dosage-related.

This paper summarized the pre-processing and determination of multi-residue of veterinary drugs in food of animal origin.Also multi-residue detection of fluoroquinolones,sulfonamides etc.at home and abroad were overviewed.In the end we looked ahead the trend of the analysis of multi-residue of veterinary drugs.

Field emitters of vertical carbon fibers on a silicon substrate are fabricated by catalytic chemical vapor deposition. After an ageing process of 150min, field emission measurement of the fibers is carried out in a vacuum chamber with a base pressure of 5.0×10−4Pa. The experimental results display that field emission performance of the carbon fibers depends strongly on the vacuum level during the experiments. After the field emission measurement, damage to the carbon fiber field emitters is observed from the scanning electron microscopic images.

A field emission device with tetrapod-like Zinc Oxide nanostructures was made by the screen printing method to observe the emission stability. The emission current recorded over time was almost kept constant for 5 hours, and the fluctuations were less than 2%. The results showed that the emission stability of tetrapod-like Zinc Oxide nanostructures is very good.

In this paper, a novel gun of RF power amplifier based on always-on cathode was described. Double hopping electron funnels are fabricated into the devices. RF modulated signal is applied on the aluminum electrode. The process of secondary electron emission, potential distribution and trajectories were simulated. In the simulation model, the primary electrons, which are low energy, emit from the ring cathode with proportional spacing

Carbon nanotubes (CNTs) have attracted great interest in the scientific field because of their unique structure, remarkable properties and potential applications. CNTs have been synthesized by methods such as arc discharge, chemical vapor deposition, laser ablation, etc. Such sustained, high-current field emission is necessary for many technological applications: for example, flat-panel field-emission displays require 10 mA/cm2, while microwave power amplifier tubes require at least 400 mA/cm2. These high-current density levels were previously obtainable only by thermionic emission above 1000 K, or lithographically fabricated tips. Field emission has been reported from other forms of carbon, however, at lower current densities (0.3 mA/cm2 for graphite, 30 mA/cm 2 for diamond)

The conversion efficiency of GaAs quantum well solar cells is calculated using detailed balance model.We discuss the effects of the quantum well structure on the cell’s conversion efficiency (for example,quasi-Fermi level variations and hot carrier transport).We also investigate the effects of the impact ionization process in the quantum well structure on the conversion efficiency.The results show that impact ionization can help increase the conversion efficiency to some extent.

This paper reports the development and the operation of field emitters with low turn on electric field based on carbon fibres. Field emitters of vertical carbon fibres on silicon substrate were fabricated by the catalyst chemical vapor deposition. The diameter of the fibres is about 3~4 mum and the height is larger than 1 mm. After one aging process of 150 minutes, field emission measurements of carbon fibres were carried out in a vacuum chamber with pressure of 5.0times10-4 Pa. The experimental results showed the turn on electric field is 1.5V/mum and the emission current density rises to 46.7mA/cm2 under the field of 2.8 V/mum. The field emission performance and stability of carbon fibres depends strongly on the vacuum level during the process of the experiments. Damages on carbon fibres were also observed because of ion bombardment

Life science is developing in high speed in the 21 st century, and the medical talent who are well educated with the consciousness of innovation are quite needed. The innovation teaching of basic chemistry course as the important essential subjects for medical students is imperative under the situation. Thus the teaching exploration and practice of the reformation of teaching material, the modernization of teaching methods, and the cultivation of innovation abilities for the medical students on long-schoding program should be carried out.

Fabrication and surface treatment of the cold cathode is a key process in making carbon nanotube field emission display(CNT-FEDs).photolithography, printing technology and supersonic processing are used to fabricate a new type of cathode. In this cathode, a flat resistance layer is prepared. The surface morphology of the cold cathode is analysed by SEM,and the emission characteristic is also measured. As the results shown, the turn-on field, current stability and emission uniformity of this cathode is improved respectively to compare to the cathode without surface treatment. This type of cathode is very suit to large area CNT-FEDs.

A carbon nanotube cathode with high emission current has been fabricated with the screen printing method.A diode structure experiment apparatus has been set up to test this cathode in the condition of vacuum less than 5×10~(-4) Pa. The diameter of the cathode is 3 mm.As a result,a total current up to 11 mA has been obtained.

本文通过对长学制医学专业有机化学开展双语教学的必要性与可行性分析,以及对双语教学方式、教材选择、师资培训、语言环境等方面的探讨,旨在探索21世纪我国高等学校医药类专业有机化学课程的创新与改革模式.

Field emission of carbon nanotubes (CNT) arrays, grown either by chemical vapor deposition (CVD) or screen printing, was studied. Its microstructures were characterized with scanning electron microscopy (SEM). The results show that the size of catalyst particles in CVD significantly affects the diameter of randomly orientated CNTs. For high emission current of CVD CNT arrays, the emission is unstable, whereas for screen printed CNT arrays, the emission is rather stable.

Objective To study the inhibitory effects of melatonin and its inhibitory mechanism on the growth of human bladder carcinoma T24. Methods The inhibitory effects of melatonin with various concentrations on the human bladder carcinoma T24 lines in vitro were determined by MTT assay. The mechanism of the inhibition was observed by flow cytometry (FCM) and transmission electron microscopy (TEM). Results The 30% inhibition concentration (IC30) value was 0.71mmol·L-1 and the 50% inhibition concentration (IC50) value was 1.20mmol·L-1. The population doubling time of T24 cells treated with melatonin at 0.71mmol·L-1 was 43.2 hours, which was significant different from that of 34.6 hours of the control group. Using FCM, we found that the cell percentage increased during the G1 phase, but decreased during the S stage. The degenerated ultra-structure of the cell treated with melatonin was also observed by TEM. Conclusion The results suggest that melatonin can inhibit the growth of human bladder carcinoma T24. The inhibitory effects of melatonin might be the prolonging of the staging from G1 to S in the cell cycle.