Sulfate ion (SO4(2-)) release from old and new cation exchange resins used in condensate polishing systems for power plants.

In this study, a dynamic cycle test, a static immersion method and a pyrolysis experiment were combined to examine the characteristics of SO4(2-) released from several new and old cation exchange resins used in condensate polishing systems for power plants. The results show that the quantity and velocity of SO4(2-) released from new and old resins tend to balance in a short time during the dynamic cycle experiment. SO4(2-) is released by 1500H (monosphere super gel type cation exchange resins) and 001 × 7 (gel type cation exchange resins) new and old cation exchange resins, the quantity of which increases according to immersion time. In the pyrolysis experiment, the quantity of SO4(2-) released from resins increases and the pH of the pyrolysis solution transforms from alkaline to acidic with an increase in temperature.

Electrocatalysis of emodin at multi-wall nanotubes.

In this article, the electrochemical behavior of emodin at multi-wall carbon nanotube modified glassy carbon electrodes (MWNTs/GCE) was studied. The result showed that MWNTs/GCE had high electrocatalytic activity for emodin. And the electrocatalytic redox process was a two-charge-two-proton process. Diffusion coefficient (D(R)) of 8.403 x 10(-5) cm(2) s(-1) of emodin was obtained. Further experiments demonstrated that the oxidative peaks increased linearly with emodin concentrations in the range of 1.0 x 10(-6) to 1.0 x 10(-4) M with a limit of detection of 3.0 x 10(-7) M. This electrochemical method was accurate and reliable, therefore, it might provide a novel way for emodin detection.

Electrochemical behavior of levodopa at multi-wall carbon nanotubes-quantum dots modified glassy carbon electrodes.

A multi-wall carbon nanotubes (MWNTs)-quantum dots (QDs) composite-modified glassy carbon electrode (GCE) was prepared. The complex was characterized by transmission electron microscopy (TEM). The electrochemical behavior of levodopa at MWNTs and QDs-modified GCEs (MWNTs-QDs/GCE) was studied by cyclic voltammetry (CV) and chronocoulometry (CC). It was found that its electrochemical behavior was a two-charge-two-proton process. The modified electrode had high electrocatalytic activity for levodopa with a standard heterogeneous rate constant of 0.595 cm s(-1), which was greatly increased compared with the values for bare GCE and individual MWNTs modified GCE. The better electrocatalytic activity for levodopa at MWNTs-QDs/GCE may due to a synergistic effect between MWNTs and QDs. This result provides a novel way to promote research on biomicromolecules at nano-dimensions.

Expression of TNF-alpha and VEGF in the esophagus of portal hypertensive rats.

AIM: To investigate the expression of tumor necrosis factor-alpha (TNF-alpha) and vascular endothelial growth factor (VEGF) in the development of esophageal varices in portal hypertensive rats. METHODS: Thirty male Sprague-Dawley (SD) rats in the model group in which a two-stage ligation of portal vein plus ligation of the left adrenal vein was performed, were divided into three subgroups (M(7), M(14), and M(21)) in which the rats were kiued on the seventh day, the 14(th) d and the 21 d after the complete portal ligation. Thirty male SD rats, which underwent the sham operation in the control group, were also separated into three subgroups (C(7), C(14) and C(21)) corresponding to the models. The expression of TNF-alpha and VEGF in the esophagus of all the six subgroups of rats were measured with immunohistochemical SP technique. RESULTS: The portal pressure in the three model subgroups was significantly higher than that in the corresponding control subgroups (23.82+/-1.83 vs 11.61+/-0.86 cmH(2)O, 20.90+/-3.27 vs 11.43+/-1.55 cmH(2)O and 20.68+/-2.27 vs 11.87+/-0.79 cmH(2)O respectively, P<0.01), as well as the number (9.3+/-1.6 vs 5.1+/-0.8, 11.1+/-0.8 vs 5.4+/-1.3 and 11.7+/-1.5 vs 5.2+/-1.1 respectively, P<0.01) and the total vascular area (78 972.6+/-3 527.8 vs 12 993.5+/-4 994.8 mum(2), 107 207.5+/-4 6461.4 vs 11 862.6+/-5 423.2 mum(2) and 110 241.4+/-49 262.2 vs 11 973.7+/-3 968.5 mum(2) respectively, P<0.01) of submucosal veins in esophagus. Compared to the corresponding controls, the expression of TNF-alpha and VEGF in M(21) was significantly higher (2.23+/-0.30 vs 1.13+/-0.28 and 1.65+/-0.38 vs 0.56+/-0.30 for TNF-alpha and VEGF respectively, P<0.01), whereas there was no difference in M(7) (1.14+/-0.38 vs 1.06+/-0.27 and 0.67+/-0.35 vs 0.50+/-0.24 for TNF-alpha and VEGF respectively, P>0.05) and M(14) (1.20+/-0.25 vs 1.04+/-0.26 and 0.65+/-0.18 vs 0.53+/-0.25 for TNF-alpha and VEGF respectively, P>0.05). And the expression of TNF-alpha and VEGF in M(21) was significantly higher than that in M(7) (2.23+/-0.30 vs 1.14+/-0.38 and 1.65+/-0.38 vs 0.67+/-0.35 for TNF-alpha and VEGF respectively, P<0.01) and M(14) (2.23+/-0.30 vs 1.20+/-0.25 and 1.65+/-0.38 vs 0.65+/-0.18 for TNF-alpha and VEGF respectively, P<0.01), but there was no difference between M(7) and M(14) (1.14+/-0.38 vs 1.20+/-0.25 and 0.67+/-0.35 vs 0.65+/-0.18 for TNF-alpha and VEGF respectively, P>0.05). CONCLUSION: In the development of esophageal varices in portal hypertensive rats, increased TNF-alpha and VEGF may be not an early event, and probably play a role in weakening the esophageal wall and the rupture of esophageal varices.

Direct electrochemistry and electrocatalytic activity of hemoglobin at CdTe nanoparticle/nafion film-modified electrode.

Water-soluble CdTe nanoparticles and hemoglobin (Hb) were immobilized on a glassy carbon (GC) electrode with Nafion. The direct electrochemistry of Hb on this surface was studied. The results indicated that CdTe nanoparticles could effectively promote the direct electron transfer of Hb at the interface of a electrode. The average surface coverage of Hb on the surface could be calculated as 2.63 x 10(-9) mol/cm2, the heterogeneous electron transfer rate constant, k, was calculated as 0.068 s(-1) and the transfer coefficient, alpha, was 0.59, further study indicated that immobilized Hb still kept its catalytic activity to H2O2 reduction. The apparent Michaelis-Menten constant was calculated to be 17.7 microM. It was also found that the modified electrode could be used as a sensor for H2O2; the linear range of detection was 5.0 x 10(-6)-4.5 x 10(-5) M, with a detection limit of 8.4 x 10(-7) M. The sensor exhibited high sensitivity, reproducibility and stability.