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HPLC determination of enantiomeric thiazolidine-2-carboxylic acid on chiral stationary phase with pre-column derivatization

Zhang Y., Peng Q., Zeng H., Yao S, Zhang Y., Song H.

Acta Chromatographica

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2013

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Vol. 25, no. 2

287--296

EN

A new high-performance liquid chromatography (HPLC) method has been developed and validated for determination of enantiomeric purity of thiazolidine-2-carboxylic acid within a short run time of less than 10 min. The method was based on pre-column derivatization of thiazolidine-2-carboxylic acid with aniline, and complete separation of enantiomers has been achieved on a Chiralcel OD-H analytical column (250 × 4.6 mm) using n-hexane-isopropanol (85:15 v/v) as mobile phase at a flow rate of 1.0 mL min-1 under UV and optical rotation (OR) detection. Detection wavelength was set at 254 nm. Then the effects of mobile phase and temperature on enantioselectivity were further evaluated. The method was validated with respect to precision, accuracy, linearity, limit of detection (LOD), limit of quantification (LOQ), and robustness. The recoveries were between 98.5 and 101.3% with percentage relative standard deviation less than 1.16%. The LOD and LOQ for the aniline derivatives of (+)-thiazolidine-2-carboxylic acid were 4.9 and 16.4 μg mL-1 and for the aniline derivatives (−)-thiazolidine-2-carboxylic acid were 5.1 and 17.2 μg mL-1, respectively.

2

A study on temperature characteristics of green silicon photodetector

Fu X., Yao S., Tao G., De M.

Optica Applicata

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2010

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Vol. 40, nr 4

935--941

EN

Green silicon photodetector is successfully developed on the substrate of n-type single-crystal (100) silicon. To improve its performance, the detector is optimized by optimizing the p-n junction depth xj and the thickness of antireflection layer to reduce dark current, shorten response time and increase sensitivity. The spectrum response SNR can be over 104 within the wavelength range of 500-600 nm and the peak of spectral responsivity is 0.48 A/W at about 520 nm. The temperature characteristics of the dark current at reverse bias and photocurrent at zero bias are emphatically investigated. Firstly, the temperature behavior of dark current at 10 V reverse bias voltage and temperature range of 253-323 K is studied. Results show that dark current is dominated by generation-recombination current Igr the temperature range of 253-283 K and it is dominated by traps tunneling current Itt at the temperature range of 283-323 K. Secondly, the temperature behavior of photocurrent at zero bias and temperature range of 213-353 K is discussed. Results show that photocurrent increases as temperature increases below room temperature and almost holds the line over room temperature. Consequently, photodetector fulfils quality requirements.

3

The effect of habitat on methane emission from an alpine wetland

Chen H., Wu N., Gao Y., Yao S., Wang Y., Tian J., Sun G., Yuan X.

Polish Journal of Ecology

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2009

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Vol. 57, nr 2

377-381

EN

Alpine wetland is a source for methane (CH[4]), an important greenhouse gas, but little is known about how this habitat influences the emission. To understand this wetland habitats were selected at the altitude of 3430 m a.s.l. (in National Wetland Nature Reserve of Zoige, Quingle - Tibetan Plateau) and the methane flux was measured with static chambers in three different sites, including hollows with Carex muliensis Hand - Mazz. and Eleocharis valleculosa Ohwi f. setosa (Ohwi) Kitagawa., grass hummocks composed of Kobresia tibetica Maxim, Cremanthodium pleurocaule R. D. Good, Potentilla bifurca L. and Pedicularis sp. We have found that in alpine wetland these habitats significantly affect CH[4] emissions in the onset (April, 2006) and peak (August, 2005) stages of growing season. Hollows covered with Carex muliensis and Eleocharis valleculosa had higher values of emission than grass hummocks built by several grass species. Slight difference of CH[4] emission was found between two kinds of hollows with Carex muliensis and Eleocharis valleculosa. These results were consistent with the change of water table, which was found best correlated with CH4 emissions (r[^2] = 0.43, P <0.01) in the peak stage of growing season. Directly measured shoot biomass and plant heights were best related to CH[4] emissions (r[^2] = 0.59, P <0.01). However, in the onset stage of growing season, variation of CH[4] emission may not be simply ascribed to changes in water table and vegetation structure.

4

Numerical simulation of heat transfer and two-phase flow in a novel heat pipe cold plate

Ma Z., Yao S.

Archives of Thermodynamics

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2009

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Vol. 30, no. 1

45-62

EN

To solve high heat flux cooling problems in case of modern electronic appliances, a novel heat pipe cold plate is designed and developed. The heat pipe cold plate is uniquely-different from normal thermosyphons, in which the acetone-aluminum heat pipe construction is composed of eight vertical heat pipe branches with their upper ends and lower ends connected with each other by two horizontal heat pipe branches, respectively, which make the working vapour and liquid flow smooth within the internal flow space of the heat pipe cold plate. In this paper, based on previous experimental and theoretical studies, a mathematical model for numerical simulations of the vapour-liquid two-phase flow and heat transfer phenomena in the heat pipe cold plate is presented. Two-fluid-model is employed to describe flow characteristics and phase interaction between vapour and liquid phases. Differential equations are solved by finite volume method and IPSA algorithm is employed to consider the vapour-liquid coupling effect. Effects of the total heating power and the cooling water flow rate on wall temperature distribution and two-phase flow heat transfer characteristics are numerically simulated. Computation results well agree with experimental results. The novel heat pipe cold plate possesses excellent heat transfer characteristics and temperature uniformity performance; it can provide a much better cooling solution for multi-heat-source and high heat-flux cooling problems than forced-convection cooling techniques. Also, numerical solution established and realized in this paper can be used as a reference.