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Localization and characterization of Fe(Ⅲ) reductase of Desulfovibrio dechloracetivorans strain SF3

WANG Jia-chen, LIN Yang, SUN Bao-lin

2009, 39(4): 337-343.

Abstract:
Both physiological and biochemical studies have demonstrate that Fe(Ⅲ)-EDTA is a favorite soluble Fe(Ⅲ) of strain SF3. The UV-visible spectra of dithionite-reduced, soluble Fe(Ⅲ) reoxidized cell extracts indicates the involvement of c-type cytochromes in Fe(Ⅲ) reduction. Fractionation experiments suggest that 87% of the Fe(Ⅲ) reducing activity is localized at soluble fraction, 74% of the Fe(Ⅲ)-reducing activity is found in the spheroplasts, which may indicate a distinct mechanism for Fe(Ⅲ) reduction. Fe(Ⅲ) reductase of strain SF3 exhibits the highest activity at 25 ℃, pH 74, and shows a great oxygen-tolerance ability.

Transdermal delivery of fusion green fluorescent protein mediated by covalently associated TD1 peptide

SUN Zheng, WEN Long-ping

2009, 39(4): 344-350.

Article Views:178 Full article PDF

Abstract:
TD1 peptide, with the amino acid sequence of ACSSSPSKHCG, has been reported to have the potential ability to facilitate transdermal delivery of macromolecules such as insulin through skin. Here we report that TD1-GGS-eGFP (TGFP), or the N-terminal TD1 modified green fluorescent protein (GFP), compared to the unmodified GFP, is more capable of transporting through skin barrier in comparison with the unmodified GFP. This finding may provide a new way for transdermal drug delivery. It can also offer a new experimental methodology for the elucidation of the mechanism through which TD1 peptide facilitates transdermal delivery.

Anticancer effect of Kean Cream in vivo and in vitro on mouse melanoma skin cancer via transdermal drug delivery

ZHAO Qi-hong, ZHANG Ying, LIU Yun, ZHOU Xu-tian, WEN Long-ping

2009, 39(4): 351-356.

Article Views:180 Full article PDF

Abstract:
To investigate the anticancer effect of Kean Cream, in which realgar nanoparticles are the main ingredient, a transdermal drug delivery system was applied to tumor tissues to increase its bioavailability and decrease its toxicity. The results show that Kean Cream could significantly suppress the proliferation and induce apoptosis of B16 melanoma cells, both in a dose-dependent manner, and tests in vivo show that Kean Cream can decrease tumor volume markedly compared to the control. Furthermore, HE stain revealed that Kean Cream can inhibit angiogenesis. Meanwhile, Kean at this concentration has little side-effect on mice. These results suggest that Kean Cream is a potential efficient transdermal anticancer agent.

Monte Carlo sampling of metabolic fluxes under thermodynamic constraints

ZHANG Yi, XIE Lu, YUAN Zi-neng

2009, 39(4): 357-364.

Article Views:179 Full article PDF

Abstract:
A new constraint-based analysis method for metabolic networks has been developed. The possible steady-states in metabolic network were treated as a thermodynamic ensemble and a potential energy function enforcing additional constraints and virtual biomass was defined. The sampling in the stead-state flux space of the central metabolic network of Escherichia coli can avoid irrational fluxes violating thermodynamic constraints and mass balance and the results were consistent with the experimental data. The proposed method is more efficient than those reported, and the flux samples have better distribution than the random sampling method. Besides, other samples can be obtained, such as ethanol optimizing, via modifying the network and the potential function, which can be helpful to metabolic engineering.

Ultraviolet emission property of undoped and Ag doped ZnO films

LIU Kai-peng, YANG Bei-fang, YAN Hong-wei, FU Zheng-ping, ZUO Jian

2009, 39(4): 365-370.

Article Views:184 Full article PDF

Abstract:
ZnO films were prepared on Si(100) substrates by ultrasonic spray pyrolysis technique. The effect of growth temperature, spray rate and Ag doping on the emission property of ZnO films was studied. Results show that appropriate growth temperature and spray rate could lead to the good quality, excellent photoluminescence property and high PL intensity ratio (R) of the UV emission to the deep-level emission. Among undoped ZnO films, the sample deposited at 500 ℃ with a spray rate of 015 mL/min has the strongest near-band edge (NBE) ultraviolet emission, with the largest R of 470. Ag doping (with the Ag:Zn atomic ratio=3%) could enhance the UV emission of ZnO films, with the R increasing to at least 700. But excessively high concentration of Ag dopant may degrade the UV luminescence property.

Mn-doped La0.1Sr0.9TiO3 for intermediate temperature NTC thermistor applications

WANG Shou-ming, ZHAO Chun-hua, LUO Wei, YANG Ping-hua, CHEN Chu-sheng

2009, 39(4): 371-374.

Article Views:165 Full article PDF

Abstract:
To explore perovkite-structured oxides for negative temperature coefficient (NTC) thermistor applications, La0.1Sr0.9TiO3 was doped by Mn. It was found that partial substitution of Ti by Mn in La0.1Sr0.9TiO3 can result in a drastic decrease in electrical resistivity ρ and thermal constant B. For La0.1Sr0.9Ti0.9Mn0.1O3, ρ at 300 ℃ was measured to be 30×102 Ω·m, and B was 5 900 K, which are all much smaller than those for the undoped sample (ρ=98×104 Ω·m, B=13 000 K). Mn doping also inhibited the drift in electrical resistivity with time. The improved electrical properties are attributed to the presence of Mn3+—O—Ti4+ network in the Mn-doped materials. The Mn-doped La0.1Sr0.9TiO3 may be used as intermediate temperature NTC thermistors.

Research on LiNixMn2-xO4 surface modification of LiCoO2 as cathode materials for Li-ion batteries

YAO Xiao-lin, ZHANG Cheng-pin, CHEN Chun-hua

2009, 39(4): 375-379.

Article Views:163 Full article PDF

Abstract:
LiCoO2 was coated with a thin layer of LiNixMn2-xO4 on its surface to improve its structural stability as cathode materials of lithium ion batteries during cycling. XRD, SEM and electrochemical tests were performed to investigate the surface morphology, structure and electrochemical properties of the LiNixMn2-xO4-coated LiCoO2. It is found that the surface modification has improved the cycle stability of the material significantly. The results show that LiCoO2 coated with a small amount (35%) of LiNixMn2-xO4 exhibits good charge-discharge properties, and retains its initial reversible capacity after 69 cycles. The layer of LiNixMn2-xO4 prevents the LiCoO2 from getting in touch with electrolyte directly, thus reducing capacity loss, and greatly increasing its plateau efficiency.

Study on sealing planar SOFC

YANG Peng-fei, XIE Bin

2009, 39(4): 380-384.

Article Views:168 Full article PDF

Abstract:
A novel composite brazing of Ag-8CuO+2YSZ was used in air to seal anode-supported planar solid oxide fuel cell (SOFC) so as to prevent leakage. The effects of YSZ （(Y2O3)008(ZrO2)092） addition on the microstructure of Ag-CuO solders joint were investigated, and the open-circuit potential (OCP) of a single cell as a function of thermal cycle number was tested to value the sealing effect. SEM microstructures of joints show that the interface between YSZ particulates and Ag-CuO matrix is tight, and that the YSZ ceramic particles are evenly distributed in the brazing metal matrix, which is conducive to improving the brazed joints performance, reducing the CTE mismatch of the brazed joint, and inhibiting the formation of holes. The single cell sealed with the above sealing material could keep good open circuit voltage of 109~102 V when operating in 750 ℃ for 15 cycles, which shows that it is suitable for planar SOFC.

2D simulation of combustion in porous medium

JIANG Hai, ZHAO Ping-hui, XU Kan, CHEN Yi-liang

2009, 39(4): 385-390.

Article Views:206 Full article PDF

Abstract:
CFD software FLUENT 62 was used to simulate propane/air premixed combustion in packed bed with user-defined scalars and user-defined functions. The two-dimensional stabilized model and simple reaction mechanism were adopted. It is concluded that, because of the wall viscosity and wall heat loss, the flame of combustion in porous medium presents an obvious 2D structure. Consequently, it is important to consider the effects of wall in designing actual porous burners.

Numerical study on the effect of secondary nucleation on spray cooling

WANG Ya-qing, LIU Ming-hou, LIU Dong, XU Kan

2009, 39(4): 391-397.

Article Views:163 Full article PDF

Abstract:
Based on the fundamental principle of spray cooling and bubble-droplet dynamics, a numerical method was developed to study the heat transfer characteristics of heated surfaces with bubbles on them, and the effect of secondary nucleation, secondary nucleation coefficient (α) and secondary nuclei range coefficient (β) on spray cooling was specially studied. The results indicate that increasing the secondary nucleation (α) could result in a rise of the heat flux, but the heat flux does not increase obviously any more when α is greater than 6. The extreme point is reached when β equals 8, and increasing or reducing the β could weaken heat transfer. Compared with the results of Cho, Ponzel, for the cases of α=6， β=3，5，8，10, it was found that β=8 can achieve the best result. Therefore, the prime α, β are 6 and 8.

Characteristics of partially shadowed serial PV module output

ZHAI Zai-teng, CHENG Xiao-fang, DING Jin-lei, ZHA Jun

2009, 39(4): 398-402.

Article Views:180 Full article PDF

Abstract:
Based on solar cell current equation and basic circuit theory, the branch output process of the partially shadowed serial solar module with bypass diode was carefully analyzed. The physical output process was divided into two phases: connection and disconnection of the bypass diode. Based on theoretical deduction, the subsection function was applied to accurately describe partially shadowed serial PV module current and power output characteristics. Finally the experiments were carried out for two serial PV module current and power output under non-uniform illumination. The experimental results demonstrate that the proposed method is correct and feasible： the subsection function can accurately describe the current and power output of partial shadowing of serial PV module with bypass diode; the single peak to power output curve, which is the basis of the traditional MPPT (maximum power point tracking), is also inexistent, so it is necessary to carry on improvement to the tracking method.

Analysis of tip effects in nanoindentation

ZHANG Tian-lin, CHEN Yu-hang, HUANG Wen-hao, WANG Xiang

2009, 39(4): 403-408.

Article Views:196 Full article PDF

Abstract:
Finite element method (FEM) was used to explore the nanoindentation process of several materials under Berkovich indenter. The simulated nanoindentation results with different tip radii were compared with experiments. A semi-empirical relation which depicts hardness with tip radius and indentation depth was derived by theoretical analysis. Results show that the measured hardness with blunt indenter increases with the tip radius and decreases with the depth of indentation. As the tip radius increases, the variation on indentation size effect becomes much more prominent. The results by theoretical analysis and FEM simulation are in good agreement. The analyzed results indicate that the tip effect in nanoindentaion is caused mainly by the underestimation of the contact area as the tip radius increases. Further results show that it is inaccurate to treat the nonideal tips as the ideal tips in theoretical analysis when the tip radius is large (R>60 nm) and the indentation depth is shallow (h≤60 nm) simultaneously, and that the hardness values tend to be overestimated.

Research on rapid quotation system in jobbing work circumstance

WEI Shen, ZHONG Xiao-qiang, WANG Yu-shan, ZHU Chang-an

2009, 39(4): 409-413.

Article Views:163 Full article PDF

Abstract:
The characteristics of product quotation in jobbing work circumstances were analyzed, and the concept of customized target vector was proposed. Based on rapid design results, a rapid quotation system was established to realize rapid quotation in jobbing work. The system has been applied to the rapid quotation for metal forming products and shown good results.

Research on the theory of the accuracy loss equality of dynamic measurement system

LIU Fang-fang, FEI Ye-tai, JIANG Min-lan

2009, 39(4): 414-418.

Article Views:177 Full article PDF

Abstract:
Based on the whole-system accuracy theory, the rule of accuracy loss was analyzed. The formula of inequality analysis were obtained according to the decomposition and tracing results of dynamic errors. Then, a uniform loss theory for dynamic measurement systems was put forward based on a principle of equality life design to make every error source a simultaneous loss for the maximum efficiency.

Experimental and numerical study on flame propagation and structure behaviors of methane-air premixed combustion in tube

HE Xue-chao, SUN Jin-hua, CHEN Xian-feng, Richard K. K. Yuen

2009, 39(4): 419-423.

Article Views:174 Full article PDF

Abstract:
The high speed Schlieren photography system and pressure sensors were used to investigate the flame propagation process of methane-air mixture in a small horizontal tube. The flame structure, propagation velocity and mixture pressure were obtained from the experiment. The results show that flame structure changes greatly in the flame propagation process, suddenly changing from a spherical laminar flame pointing forward to a V shape turbulent flame forming a cusp toward the burned gas. In this process, the velocity decreases but the pressure increases continuously. With the k-ε turbulent combustion model, unsteady premixed methane flame in a 2D matrix burner was numerically simulated. The characteristics of flame propagation and flame structure variation qualitatively agree with the experimental data very well.

A numerical study on smoke layering plugholing under mechanical extraction in a long channel

JIANG Ya-qiang, HUO Ran, HU Long-hua, JI Jie, YANG Dong, WANG Hao-bo

2009, 39(4): 424-428.

Article Views:167 Full article PDF

Abstract:
In a long model channel under mechanical extraction, the flow pattern, vertical temperature distribution and depth of the smoke layer below the extraction vent were analyzed by numerical modeling. The variations of the depth and temperature under different mechanical extraction rates were quantitatively described. The results show that plugholing occurs in the long channel when smoke extraction rate increases to some relative high levels, causing the efficiency of the mechanical extraction system to be reduced.

Design of a natural gas leak detection system with tunable diode laser absorption spectroscopy

ZHU Yu-quan, QIAO Li-feng, ZHANG Qi-xing, CAI Ting-li, WANG Jin-jun, ZHANG Yong-ming

2009, 39(4): 429-434.

Article Views:209 Full article PDF

Abstract:
Tunable diode laser absorption spectroscopy (TDLAS) was used for natural gas leakage detection, and its principle was analyzed. The selection of the diode laser and the photodiode for natural gas leakage detection system and the characteristics of the laser diode and photodiode were introduced. The measurement results show that the lowest gas detection level is 27×10-6 and gas change times per minute is 93~113 times/min. The gas concentration along the natural gas line with number modulation was obtained, and a natural gas line leakage detection method was proposed.

Improvement of stability of Raman backscattering optical fiber temperature fire alarm system

WANG Xin-qun, HE Guo-min, DING Bang-qin, HUANG Xin

2009, 39(4): 435-439.

Article Views:157 Full article PDF

Abstract:
The parameters affecting the stability of Raman backscattering optical fiber temperature fire alarm systemwere analyzed, and methods to improve stability were applied. A new wavelength division multiplier (WDM) was used to extract the Raman scattering signal from a data fiber, which can reduce peak insertion loss and increase isolation significantly. Measures were taken to keep APD (avalanche photo diode) working at a constant temperature and at a low reverse voltage so as to maintain the avalanche multiplication at a constant gain. A special data acquisition card for Raman signal processing was adopted to improve time resolution. The result shows that the stability of the system was improved with the application of these measures.

Influence of different electron donors on metal reduction by Desulfovibrio dechloracetivorans strain SF3

LIN Yang, WANG Jia-chen, CHU Cheng-cao, SUN Bao-lin

2009, 39(4): 440-446.

Article Views:150 Full article PDF

Abstract:
Chlororespiring, sulfate-reducing bacterium Desulfovibrio dechloracetivorans strain SF3 is capable of dissimilatively reducing Fe(Ⅲ), Cr(Ⅵ) and Co(Ⅲ). Acetate, ethanol, hydrogen, formate, pyruvate, lactate and citrate can be used as electron donors for soluble Fe(Ⅲ) reduction, whereas poorly crystalline Fe(Ⅲ)-oxide can be reduced only in the presence of pyruvate or H2. Our experimental results show that the ratio of Fe(Ⅲ)-EDTA reduced to acetate consumed is 776±035, and no growth companied the Fe(Ⅲ) reduction in the presence of acetate. Reduction of Cr(Ⅵ) and Co(Ⅲ) can be stimulated by hydrogen, pyruvate and lactate, but addition of acetate had no effect. To our knowledge, it is the first report that an SRB (sulfate-reducing bacteria) can utilize acetate as an electron donor for soluble Fe(Ⅲ) reduction but not for insoluble Fe(Ⅲ), and Cr(Ⅵ), Co(Ⅲ) reduction, which indicates that a complex electron transfer system is hired by strain SF3 for metal reduction.

2009 Vol. 39, No. 4

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