Biomedical subjects

Jianguo Yu

Publications and source records attributed to Jianguo Yu.

9 recordsLinked to original sources

PubMed2006

Coverage dependence and hydroperoxyl-mediated pathway of catalytic water formation on Pt (111) surface.

Hydrogen oxidation on Pt (111) surface is modeled by density functional theory (DFT). Previous DFT calculations showed too large O2 dissociation barriers, but we find them highly coverage dependent: when the coverage is low, dissociation barriers close to experimental values (approximately 0.3 eV) are obtained. For the whole reaction, a new pathway involving hydroperoxyl (OOH) intermediate is found, with the highest reaction barrier of only approximately 0.4 eV. This may explain the experimental observation of catalytic water formation on Pt (111) surface above the H2O desorption temperature of 170 K, despite that the direct reaction between chemisorbed O and H atoms is a highly activated process with barrier approximately 1 eV as previous calculations showed.

Journal Article↗

PubMed2006

Gray correlation analysis and prediction models of living refuse generation in Shanghai city.

A better understanding of the factors that affect the generation of municipal living refuse (MLF) and the accurate prediction of its generation are crucial for municipal planning projects and city management. Up to now, most of the design efforts have been based on a rough prediction of MLF without any actual support. In this paper, based on published data of socioeconomic variables and MLF generation from 1990 to 2003 in the city of Shanghai, the main factors that affect MLF generation have been quantitatively studied using the method of gray correlation coefficient. Several gray models, such as GM(1,1), GIM(1), GPPM(1) and GLPM(1), have been studied, and predicted results are verified with subsequent residual test. Results show that, among the selected seven factors, consumption of gas, water and electricity are the largest three factors affecting MLF generation, and GLPM(1) is the optimized model to predict MLF generation. Through this model, the predicted MLF generation in 2010 in Shanghai will be 7.65 million tons. The methods and results developed in this paper can provide valuable information for MLF management and related municipal planning projects.

China↗

PubMed2005

QSAR analysis of soil sorption coefficients for polar organic chemicals: substituted anilines and phenols.

Based on descriptors of n-octanol/water partition coefficients (logKow), molecular connectivity indices, and quantum chemical parameters, several QSAR models were built to estimate the soil sorption coefficients (logKoc) of substituted anilines and phenols. Results showed that descriptor logKow plus molecular quantum chemical parameters gave poor regression models. Further study was performed to improve the QSAR model by using artificial neural networks (ANNs). It showed that ANN model with suitable network architecture could make a better agreement between predicted and measured values of the soil sorption coefficients. The quality of the QSAR models confirmed the suitability of ANN to predict the soil sorption coefficients for polar organic chemicals of substituted anilines and phenols.

Adsorption↗

PubMed2002

Effects of short-range attraction in metal epitaxial growth.

The effects of short-range attraction in metal epitaxial growth are studied. Our results indicate that even at normal incidence, the short-range attraction of depositing atoms to step edges can significantly increase the selected mound angle and surface roughness for typical energies used in epitaxial growth. Our results also lead to a picture of the process of deposition near step edges that is quite different from the standard downward funneling picture. Results for the dependence of the uphill current on incident atom kinetic energy and substrate temperature are also presented.

Journal Article↗

PubMed2002

Dynamical scaling behavior in two-dimensional ballistic deposition with shadowing.

The dynamical scaling behavior in two-dimensional ballistic deposition with shadowing is studied as a function of the angular distribution of incoming particles and of the underlying lattice structure. Using a dynamical scaling form for the surface box number, results for the scaling of the surface fractal dimension are also presented. Our results indicate that, in addition to the usual self-affine universality class corresponding to vertical deposition, there exist at least two additional universality classes characterized by distinct values of the coarsening and roughening exponents p and beta describing the evolution of the lateral feature size and surface roughness with film thickness, as well as the surface fractal dimension D(f). For the case of a uniform angular distribution corresponding to an anisotropic flux, we find p=beta=1 and D(f) approximately 1.7. However, for ballistic deposition with an isotropic flux (corresponding to a "cosine" angular distribution), we find p approximately 2/3 and D(f) approximately 1.5 while the effective roughening exponent beta approximately 0.52-0.64 was found to be slightly lattice dependent. In both cases, anomalous scaling of the height-height correlation function is also observed. In contrast, vertical deposition leads to a self-affine surface with p=2/3, beta=1/3, and D(f)=1. The asymptotic scaling behavior appears to depend on the behavior of the angular distribution at large angles but does not depend on other details. An analysis that clarifies the relationship between the launch angle distribution used in the simulations and the flux distribution is also presented.

Journal Article↗

PubMed2002

Scaling behavior of the surface in ballistic deposition.

Using a dynamical scaling form for the surface fractal dimension as well as efficient algorithms for the simulation and analysis of the surface in three-dimensional ballistic deposition, we show that while the top of the surface is self-affine, the complete surface including overhangs has fractal dimension D(f) approximately 3. The existence of such a fractal surface is a consequence of the difficulty of closing off voids in three and higher dimensions. By studying a modified ballistic deposition model in which sticking is allowed with a given probability p, we show that the surface undergoes a phase transition from fractal to compact at a finite value of p. Our results also have implications for understanding the surface morphology in sedimentary rocks and low-temperature thin films.

Journal Article↗

PubMed2002

[Wavelet feature extraction and classification of Doppler ultrasound blood flow signals].

The maximum frequency waveforms of Doppler ultrasound blood flow signals were analyzed using a multi-scale wavelet transform. The variation of maxima of wavelet transform modulus under various scales was extracted from the time-scale representation. This novel approach was applied to the analysis of Doppler signals from carotid blood flow. It was found that the shape of this variation from cases with normal cerebral vessels differed from those associated with abnormal cases. The curve was fitted by a polynomial, and its coefficients were put into a back-propagation (BP) neural network to make a classification. The clinical experiments showed that this approach got good performance and could be a new means in the clinical diagnosis of cerebral vascular disease.

Algorithms↗

PubMed2002

[The effects of hepatitis E virus superinfection on patients with chronic hepatitis B: a clinico-pathological study].

OBJECTIVE: To observe the effect of hepatitis E virus (HEV) superinfection on hepatic lesion and hepatitis B virus (HBV) replication in patients with chronic hepatitis B (CHB). METHODS: Totally 122 patients with CHB were enrolled in this study. They were tested for anti-HEV IgM and IgG in serum, amount of HBV DNA in serum and liver tissue obtained by liver biopsy and HBcAg expression in liver tissue. Other parameters such as ALT, total bilirubin (TBil), albumin (A) and globulin (G), gamma-electrophoretic protein (gamma-EP), prothrombin activity (PTA) were also measured. 21 of the 122 patients (17.2%) were found to have HEV superinfection and the remaining 101 were not. Repeat liver biopsy was performed after 1 year in 7 patients with HEV superinfection and 14 patients without. Moreover, HBV DNA amount in serum from 8 HBeAg negative patients with HEV superinfection were tested dynamically in acute and recovery stage of HEV infection. RESULTS: Comparison of the data from the 21 patients with HEV superinfection and 101 without showed that there was no significant difference in the level of A/G ratio (1.74 +/- 0.50 vs. 1.83 +/- 0.37) and gamma-EP [(24.18 +/- 6.36)% vs. (22.27 +/- 4.59)%, P > 0.05]. However, the level of ALT [(244.61 +/- 81.07) U/L vs. (143.87 +/- 47.69) U/L] and TBil [(88.24 +/- 28.54) micro mol/L vs. (46.16 +/- 17.13) micro mol/L] was significantly higher (P < 0.05), but that of PTA lower in the group with HEV superinfection than in the group without superinfection [(58.57 +/- 17.44)% vs. (72.52 +/- 12.25)%, P < 0.05]. So were the amount of HBV DNA in serum [(5.45 +/- 1.86) copies/ml vs. (6.59 +/- 1.28) copies/ml, P < 0.05] and liver tissue [(6.96 +/- 2.52) copies/g vs. (8.47 +/- 1.79) copies/g, P < 0.05] as well as HBeAg and HBcAg positive rates (8/21 vs. 64/101; 9/21 vs. 67/101, P < 0.05). Pathologically, the hepatic inflammatory activity was more severer in patients with HEV superinfection, but the severity of fibrosis was not significantly different. There was no difference in the severity of inflammatory activity and stage of fibrosis between the 7 patients with HEV superinfection and the 14 patients without as well as before and after 1 year of treatment. The amount of HBV DNA and HBeAg positive rate in serum from recovery stage of HEV infection were higher than those of acute stage. CONCLUSIONS: HEV superinfection leads to activation of hepatic pathological changes and worsens the inflammatory activity. Moreover, HEV superinfection inhibits HBV replication, but it may not be long-lasting.

Adult↗

PubMed2002

[Relationship between amount of HBV DNA in serum/liver tissue and hepatitis G virus (HGV) infection in patients with chronic hepatitis B].

OBJECTIVE: To observe the relationship between the amount of HBV DNA in serum/liver tissue and HGV infection in patients with chronic hepatitis B (CH-B) for exploring the effect of HGV infection on hepatitis B virus (HBV) replication of CH-B. METHODS: HGV RNA in serum, HGV nonstructural region 5 (NS5) antigen (HGV Ag) in liver tissue and the amount of HBV DNA in serum, liver tissue were detected for 56 patients with CH-B by reverse transcription-polymerase chain reaction (RT-PCR) assay, peroxidase antiperoxidase (PAP) immunohistochemical method and fluorescence quantitative PCR assay, respectively. Then the relationship between HGV Ag expression in liver tissue and HGV RNA expression in serum was analysed and the amount of HBV DNA in serum and liver tissues from the serum HGV RNA or liver tissue HGV Ag positive patients were compared with those of the serum HGV-RNA or liver tissue HGV Ag negative patients, respectively. RESULTS: Ten (17.9%) and eight (14.3%) patients were positive for serum and liver tissues,respectively.HGV RNA expression in serum was closely related to HGV Ag expression in liver tissues, but there was HGV RNA in serum from some of the liver tissues HGV Ag negative patients ?cases of HGV RNA and HGV Ag positive or negative,HGV RNA positive but HGV Ag negative, HGV RNA negative but HGV Ag positive, respectively: 5,43,5,3,(P<0.01). There was no significant difference in the amount of HBV DNA in serum and liver tissues between HGV RNA or HGV Ag positive and negative patients (P>0.05). CONCLUSIONS: HGV infection may not affect HBV replication. Liver is the site of HGV replication, but HGV probably also replicates in extrahepatic tissues. HGV hepatic pathogenicity is probably mild and further studies are still needed.

Adult↗