Computational modeling of gas-surface interaction

In this study, a new computational modeling of the gas-surface interaction is proposed to explain the results of the scattering experiments of molecular beams from solid surfaces, especially from industrial surfaces. The characteristic feature of the model is to settle the adsorbed gas layer and the collision layer which involve adsorbed molecules and surface molecules, respectively. Incident molecules experience force due to the gas-solid potential gradient, changing their trajectories which is computed by Molecular Dynamics method. The gas molecules are scattered from the surfaces after collisions with adsorbed or surface molecules. The simulated results are compared with the experimental ones: i.e., flux distributions, TOF spectra and the average energy of scattered molecules.     

Some characteristics of a miniature neutron spectrometer

Some characteristics of an NE213 miniature spherical spectrometer for in-assembly fast-neutron spectrometry were measured. As the bubbling time changed, the pulse-height did not change appreciably, but the n?γ discrimination characteristics changed considerably. As the count rate changed, the pulse-height did not change appreciably, and the change of the n?γ discrimination characteristics was acceptable. The neutron response function was measured to be almost isotropic except for the backward direction.     

Reduced turn-on delay time in 1.3-/spl mu/m InGaAsP-InP n-type modulation-doped strained multiquantum-well lasers with a buried heterostructure

A reduction in both the threshold current and carrier lifetime is demonstrated, for the first time, in an n-type modulation-doped InGaAsP strained multiquantum well laser with a buried heterostructure. Threshold current and carrier lifetime is reduced by 10% and 15%, respectively, as compared with a undoped MQW laser, which results in a 35% decrease in the turn-on delay time. This confirms the suitability of this type of laser for use as a light source for high-density parallel optical interconnection.     

杨桃多酚氧化酶的部分纯化及其特性研究

杨桃多酚氧化酶粗酶液经过DEAE-Toyopearl650M离子交换柱层析,Butyl-Toyopearl650M疏水柱层析后,被纯化了21.6倍,回收率为45.2%。该酶能迅速地催化焦性没食子酸的酶促氧化反应,而对邻苯二酚、间苯二酚、对苯二酚和绿原酸则完全无催化活性。该酶对焦性没食子酸的Km值为7.92mmol/L,其最适pH为8.0,pH稳定性范围在pH4.0-11.0,最适温度为60℃,热稳定性相对较高,在≥90℃加热30min后仍残留约9%的酶活性。该酶的最佳抑制剂是抗坏血酸,其次是NaHSO3和盐酸-L-半胱氨酸,Cu2+、Zn2+、Ca2+等金属离子对该酶也有一定的抑制作用。     

响应面法优化菊黄东方鲀肌肉多肽制备工艺

为优化菊黄东方鲀肌肉多肽酶解法制备工艺,该实验选择响应面法对菊黄东方鲀肌肉制备工艺进行研究.该实验用酸性蛋白酶、碱性蛋白酶、胰蛋白酶、中性蛋白酶、风味蛋白酶、木瓜蛋白酶这6种蛋白酶对菊黄东方鲀肌肉进行酶解,以水解度为指标,进行蛋白酶的筛选,并选择风味蛋白酶进行后续实验.通过单因素法研究料液比、pH、酶解时间、温度、酶添...     

Confirmation of non-permitted dyes detected in Akasu (red vinegar) by LC/MS

Suitable liquid chromatography/mass spetrometry (LC/MS) conditions were examined for Amaranth, Red 2G (R2G), Azo Rubine (Azo), Fast Red E (FRE) and Brilliant Blue FCF, which were detected in Akasu, a red vinegar made in Hong Kong from sake lees, on both thin layer chromatography (TLC) and photodiode array high-performance liquid chromatography (PDA-HPLC). Molecular-related ions for each dye were detected with excellent sensitivity by LC/MS using electro-spray ionization with negative ion mode, capillary voltage 3.00 kV, cone voltage 50 V and desolvation temperature 400 degrees C. LC/MS analysis of refined Akasu under these conditions enabled us to obtain clear mass spectra of R2G, Azo and FRE, which were present at trace levels in the Akasu. The results were consistent with those from TLC and PDA-HPLC. These experiments suggested that LC/MS analysis is applicable for confirmation of dyes in food.     

Decomposition Kinetics of Glucose and Fructose in Subcritical Water Containing Sodium Chloride

The kinetics of the decomposition and isomerization of glucose and fructose in pure water and water containing sodium chloride (1–20 % w/w) under subcritical conditions at 180–220 °C was investigated. The addition of sodium chloride in subcritical water accelerated the decrease of glucose, and the rate was expressed by the Weibull equation. Although the isomerization of glucose to fructose was observed in parallel with decomposition, the yield of fructose was lower at higher sodium chloride concentrations. Mannose was also formed from glucose with very low yield. It was seen that fructose decomposed much faster than glucose, in pure and salty subcritical water. The decomposition of fructose obeyed first-order kinetics in the initial stages of the reaction and could be expressed by the autocatalytic model in the later stages. The formation of glucose and mannose from fructose was not observed under any of the conditions investigated.     

Determination of synthetic food dyes in food by capillary electrophoresis

A method for the determination of 12 synthetic food dyes (Amaranth, Erythrosine, Allura Red AC, New Coccine, Phloxine, Rose Bengal, Acid Red, Tartrazine, Sunset Yellow FCF, Fast Green FCF, Brilliant Blue FCF, Indigo Carmine) in food was developed using capillary electrophoresis (CE) with photodiode array detection. The dyes were extracted with water and 0.5% ammonia-ethanol (1:1) mixture, and cleaned up using solid-phase extraction (Sep-Pak Plus tC18). The dyes were eluted with methanol from the cartridge. The dyes were separated by CE on a bubble cell fused-silica capillary (72 cm to the detector, 75 microm i.d.) using 20% acetonitrile in a mixture of 10 mmol/L potassium phosphate, monobasic and 5 mmol/L sodium carbonate (pH 10.0) as the running buffer. Identifications of the dyes were performed on the basis of the migration time and the absorbance spectrum of each peak. The coefficients of variation of the migration times and the peak areas were 0.28-0.62% and 1.84-4.30%, respectively (n = 5). The identification limits using the absorbance spectra of the dyes were 10 microg/mL for Brilliant Blue FCF and Fast Green FCF, and 5 microg/mL for the other 10 dyes. The recoveries of the 12 dyes from pickles, soft drinks and candies at the level of 10 microg/g were 70.0-101.5%. The method was applied to the analysis of dyes in foods. The dyes detected by CE were in agreement with those detected by paper chromatography.