Showing papers by "Xiang Zhang published in 2001"

Polypyrrole-Coated Granules for Humic Acid Removal

Abstract: Granules with positive surface charges were prepared by coating glass beads with polypyrrole (PPy). The coated glass beads were found to possess high positive zeta potentials over a wide range of pH values. Batch and fixed bed humic acid adsorption experiments using the coated glass beads as adsorbents were conducted. Scanning electron microscope (SEM) was used to examine the surface morphology of the coated glass beads before and after humic acid adsorption. X-ray photoelectron spectroscopy (XPS) was applied to assess the protonation and charge transfer of the PPy coating with and without adsorbed humic acid. SEM images showed that the PPy coating considerably increased the surface roughness of the granules and a significant amount of humic acid was adsorbed on the PPy coating. From XPS analysis, it was found that 28% of the nitrogen atoms in the PPy coating were protonated, leading to a highly positively charged surface at pH<10.5. The results also showed that the amount of protonated nitrogen atoms decreased by up to 25% due to humic acid adsorption, suggesting that humic acid uptake by the PPy-coated glass beads was affected at least partly by charge neutralization. Humic acid adsorption also resulted in a reverse of the positive zeta potential of the PPy coating, indicating the importance of macromolecular adsorption in the process. The adsorption equilibrium data can be fitted with either the Langmuir or the Freundlich expression. Both pH and ionic concentration were found to affect the extent of humic acid adsorption by the PPy-coated granules.

Polymeric micromechanical components with tunable stiffness

Abstract: We present a microstereolithographic technique that enables the manufacturing of polymeric components for microelectromechanical systems. Model microstructures were fabricated in the form of end-supported microbeams (10 μm in diameter), in order to characterize the mechanical properties of the produced structures at the micron scale. The flexural modulus of these microbeams was measured by atomic force microscopy, using cantilevers with attached metal spheres, and employed in a three-point bending geometry. Postfabrication treatment of the microstructures allows for the tailoring of their stiffness.

Zircon U-Pb dating of the metamorphic rocks of different grades from the southern part of the Dabie terrain in China

Abstract: Zircon U-Pb dating was carried out for a number of the metamorphic rocks of different grades in the southern part of the Dabie terrain. They include regional orthogneisses and enclosed phyllite in South Dabie unit as well as schist and amphibolite in Susong metamorphic belt. The ages of one orthogneiss sample indicate an emplacement time of its protolith at Neoproterozoic (576±49Ma) and a metamorphic event at 245±33Ma. Ages of 400 to 500Ma were obtained for the samples of the orthogneiss and phyllite in South Dabie ultrahigh pressure terrain as well as schist and amphibolite in Susong metamorphic belt suggesting that these rocks were affected by a tectono-thermal event at Early Palaeozoic. This implies that the rocks were not subducted to mantle depths by plate subduction and did to suffer resetting of U-Pb isotopic system by ultrahigh pressure metamorphism at Triassic.

Ab initio study on the rate constants of SiCl4+ H → SiCl3+ HCl

Abstract: The reaction SiCl4 + H → SiCl3 + HCl is studied using an ab initio dynamic method. The direct chlorine abstraction of reaction processes ia a C3v symmetry transition state is calculated by the intrinsic reaction coordinate (IRC) method at the UMP2/6-311G(d,p) level. The forward and reverse barriers are refined by UMP4(SDTQ) and UQCISD(T) single point energy calculations using the same basis set of 6-311G(d,p). The forward barrier is calculated to be 24.34 kcal mol−1 at the UMP4(SDTQ) level and 22.62 kcal mol−1 at the UQCISD(T) level, while the reverse barrier is 22.46 and 21.90 kcal mol−1, respectively. The enthalpy of reaction is calculated to be 1.94 kcal mol−1 at the UMP4(SDTQ) level and 0.72 kcal mol−1 at the UQCISD(T) level. The forward rate constants in the temperature range 1500–1800 K are calculated by the conventional and variational transition state theory (CVT) with small-curvature tunneling (SCT) correction. The variational effect is important for the calculation of forward rate constants but the SCT correction is small. The CVT and CVT/SCT rate constants of the forward reaction at the UMP4(SDTQ) and UQCISD(T) levels are consistent with the lower limit of the experimental result. However, the theoretical activation energies in the temperature range 1500–1800 K, 28.43 kcal mol−1 at the UMP4(SDTQ) level and 27.10 kcal mol−1 at the UQCISD(T) level, are much higher than the experimental value, 9.54 ± 5.17 kcal mol−1. The theoretical temperature dependence of the rate constants differs from the experimental result.

[Establishment of model of aristolochic acid-induced chronic renal interstitial fibrosis in rats].

Abstract: OBJECTIVE To study chronic renal interstitial fibrosis induced by aristolochic acid (AA) in animal models. METHODS Female Wistar rats were divided into two groups: AA group (n = 42) peritoneally injected with AA (5 mg.kg-1.d-1) for 16 weeks and control group (n = 5) peritoneally injected with normal saline (2 ml/d) for 16 weeks. The body weight of rats was taken. At week 8, 12, 16, and 24 six rats were killed in the AA group. The five rats in the control group were killed at week 24. Specimens of lood and urine were taken before the animals were killed. Specimens of renal tissue were taken after the animals were killed. Twenty-four hour urine protein, urine beta 2 microglobulin (beta 2-MG), and renal function were tested regularly. Pathological examination, including tubulo-interstitial area calculation, was made to the renal specimens. RESULTS The body weight of rats in AA group became significantly lower than that of the control rats after 16 weeks' AA injection (P < 0.01). The blood urea nitrogen (BUN) and serum creatinine (Scr) in AA group increased significantly than those of the control group at the 16th, 20th, and 24th weeks (P < 0.05). Optical microscopy showed tubular-interstitial damage in AA group in 16 weeks. Renal tubular atrophy and multifocal renal interstitial fibrosis were shown in 24 weeks. The area of renal tubule increased and the area of the lumen remarkably decreased at week 16 compared with those in the control group. The area of renal tubule decreased remarkably and the area of renal interstitial greatly in the AA group at week 24. Electrical microscopy showed increase of primary and secondary lysosomes and diasappearence of part of brush border of tubular endothelial cells at week 16, and accumulation of secondary lysosome in cytoplasm at weeks 20 and 24 in the AA group. Histoimmunofluorescence showed that IgG, IgA, IgM, C3, and C1q were negative in the renal tissue of experimental animals. CONCLUSION Animal models with chronic renal tubuloointerstitial nephropathy induced by aristolochic acid were successfully established. Aristolochic acid may have chronic toxicity to renal tissues, and cause chronic renal interstitial fibrosis in rats.

[The sensitized reaction of non-ionic microemulsion on the determination of trace Ni(II) by fluorescence quenching method with salicyfluorone].

Abstract: A new selective and sensitive spectrofluorimetric method in non-ionic microemulsion for the determination of trace Ni(II) in water has been developed. This method is based on the quenching of fluorescence of Triton X-100/n-C5H11OH/n-C9H20/H2O microemulsion system due to the formation of complex Ni(II)-SAF-Triton X-100. The results show that there is a linear relationship in the rang of 0.5-2.5 ng.25 mL-1 for Ni(II). The sensitivity in microemulsion is higher than that in micelle. Satisfactory results are obtained for Ni(II) in water sample.

Urodynamic characteristics of patients with tethered cord syndrome and its clinical significance

Abstract: OBJECTIVE To evaluate the urodynamic characteristics of children with tethered cord syndrome (TCS) and its clinical significance METHODS We conducted urodynamic studies in 94 cases of TCS who underwent microsurgical release within one week preoperatively and 3 to 6 months postoperatively RESULTS 80 out of 94 (851%) children with TCS presented with lower urinary tract symptoms Neuropathic injuries were found both in patients in group A (with lower urinary tract symptoms) and in 11 out of 14 patient in group B (without lower urinary tract symptoms) The maximum urethral closing pressure (MUCP) and maximum detrusor pressure (MDP) were significantly lower in group alpha (without upper urinary tract injury), which were 45 cm H(2)O +/- 18 cm H(2)O and 27 cm H(2)O +/- 15 cm H(2)O respectively, than in group beta (with upper urinary tract injury), which were 69 cm H(2)O +/- 24 cm H(2)O and 44 cm H(2)O +/- 17 cm H(2)O respectively, while bladder compliance (BC) in group alpha (56 cm H(2)O +/- 09 ml/cm H(2)O) was significantly higher than in group beta (25 ml/cm H(2)O +/- 12 ml/cm H(2)O) MUCP, MDP and BC were improved in group I (primary TCS) after cord untethering, 32 cm H(2)O +/- 14 cm H(2)O, 21 cm H(2)O +/- 12 cm H(2)O, 95 ml/cm H(2)O +/- 13 ml/cm H(2)O postoperatively and 63 cm H(2)O +/- 245 cm H(2)O, 37 cm H(2)O +/- 156 cm H(2)O, 51 ml/cm H(2)O +/- 08 ml/cm H(2)O preoperatively respectively, while in group II remained unchangeable CONCLUSION Urodynamic studies are effective methods to identify neuropathic characteristics of lower urinary tract symptom in children with TCS and to find neuropathic injury during subclinical period According to urodynamic studies, increase of MUCP and DP and decrease of BC are high risk factors of vesicoureteral reflux and upper urinary tract injury Microsurgical release can improve bladder function in primary TCS, while do no good to bladder function in secondary TCS

Molecular-beam-epitaxy growth and luminescence properties of Nd3+-doped LaF3/CaF2 thin films

Abstract: Nd3+-doped LaF3 heteroepitaxial waveguide films on two oriented CaF2 substrates were grown by the molecular-beam-epitaxy method. The spectroscopic properties of Nd3+ in the epitaxial films have been studied by using a tunable Ti:sapphire laser. Efficient IR emissions have been detected at 1.06, 0.86, and 1.32 nm ranges. The influences of substrate orientation, Nd3+ concentration, and temperature on the luminescence properties were investigated. By using a prism-coupling technique, waveguided luminescence has been measured at room temperature. Furthermore, laser emission at 1.06 μm was obtained at room temperature with a 790 nm laser pump.

Sol-gel synthesis and emission characterization of Mn/sup 2+/:Zn/sub 2/SiO/sub 4/ thin films

Abstract: This paper summarizes the results on structural details and photoluminescence spectra of Mn/sup 2+/:Zn/sub 2/SiO/sub 4/ thin films deposited on SiO/sub 2//Si in sol-gel process annealed at 1000/spl deg/C in different environments (N/sub 2/, O/sub 2/ & vacuum) for their optoelectronic applications.