Showing papers by "Hua Zhang published in 2000"
TL;DR: In this article, the authors provide a convenient method for fabricating architectures of Au nanoparticles on solid substrate, with precise position and density control, and a strategy is to modify Au substrate with s...
Abstract: This paper provides a convenient method for fabricating architectures of Au nanoparticles on solid substrate,with precise position and density control. Our strategy is to modify Au substrate with s...
166 citations
TL;DR: In this article, the stiffness and adhesion properties of individual polyphenylene dendrimers have been investigated by spin coating on a mica surface, and subsequently imaged by noncontact atomic force microscopy.
Abstract: Well-separated, individual polyphenylene dendrimer molecules have been prepared by spin coating on a mica surface, and subsequently imaged by noncontact atomic force microscopy (NCAFM). The observed height is in good agreement with the size of a single dendrimer molecule, as calculated by molecular dynamics simulation. By using pulsed force mode (PFM) AFM, stiffness and adhesion properties of individual polyphenylene dendrimers have been studied. They could be related to the molecular structure and the chemical nature of the outer surface of the dendrimers and the thin film of water adsorbed on mica when imaged under ambient conditions. Finally, by changing the concentration of the spin-coating solution, two different kinds of aggregates have been characterized.
60 citations
TL;DR: In this paper, a self-assembled monolayer (SAM) patterned with COOH and CH3 groups was used as the model surface, and its local dissociation property was studied by both chemical force titration and contact angle titration.
Abstract: An experimental approach for probing the resolution of chemical force titration is reported here. A self-assembled monolayer (SAM) patterned with COOH and CH3 groups was used as the model surface, and its local dissociation property was studied by both chemical force titration and contact angle titration. The dissociation constant (pK1/2) estimated by chemical force titration was found to be sensitive to the surface location. In the COOH region, chemical force titration gave a pK1/2 value of 5.4, identical with the value obtained on a pure, unpatterned COOH SAM, while in the CH3 region, the force curves varied greatly from site to site even in the same pH solution, indicating the mixed film nature being originated from the microcontact printing process. In contrast, contact angle titration generates a fixed pK1/2 value of 11.0 on the patterned surface, completely different from the force titration results. This study demonstrates that chemical force titration indeed has a spatially resolved capability, wi...
49 citations
TL;DR: Tb3+ doped Zn2SiO4 films have been deposited on SiO2 buffered Si wafers by sol-gel method as discussed by the authors, which revealed that these films were composed of nanometer-size grains with a Willemite structure and had smooth surfaces.
48 citations
TL;DR: Geometrically defined gold microelectrode arrays are fabricated, in which a self-assembled monolayer of hexadecylmercaptan acts as passivation layer and is region-selectively formed by microcontact.
Abstract: Geometrically defined gold microelectrode arrays are fabricated, in which a self-assembled monolayer of hexadecylmercaptan acts as passivation layer and is region-selectively formed by microcontact...
42 citations
TL;DR: In this article, two different types of aggregated polyphenylene dendrimer molecules, G2Td(COOH)16 and G4-Td, obtained by spin coating a dilute solution onto freshly cleaved mica surfaces, and their adhesion properties were measured by pulsed force mode (PFM) AFM.
Abstract: Two different types of aggregated polyphenylene dendrimer molecules, G2Td(COOH)16 and G4-Td, obtained by spin coating a dilute solution onto freshly cleaved mica surfaces, and their adhesion properties were measured by pulsed force mode (PFM) AFM. The adhesion properties could be related to the chemical nature of the outer surface of the dendrimers and the mica surface, and the thin film of water adsorbed on mica when imaged under ambient conditions. Most importantly, from the adhesion image of mixed aggregates of G2Td(COOH)16 and G4-Td, as measured by PFM-AFM, the two different aggregated dendrimers can be easily discriminated.
31 citations
TL;DR: In this paper, a structural transition at molecular scale was observed in an organic p-nitrobenzonitrile (PNBN) thin film using scanning tunneling microscopy (STM).
Abstract: We present a direct observation of a structural transition at molecular scale in an organic p-nitrobenzonitrile (PNBN) thin film using scanning tunneling microscopy (STM). STM images clearly show an ordered molecular structure of unrecorded regions in the films, while the PNBN molecular arrangements are disordered in the recorded regions. The current–voltage (I–V) measurements from the STM demonstrate a great increase of the conductance transition in the recorded regions after the voltage pulses. Those results suggest that the recording mechanism may be due to a crystalline structural transition, which is consistent with our previously proposed mechanism in another organic system for ultrahigh density data storage.
25 citations
TL;DR: In this paper, the displacement adsorption process of 4-mercaptopyridine (4-MP) on trisodium citrate preadsorbed gold surface in aqueous solution was studied using atomic force microscopy (AFM).
Abstract: The displacement adsorption process of 4-mercaptopyridine (4-MP) on trisodium citrate preadsorbed gold surface in aqueous solution was studied using atomic force microscopy (AFM). The measurement was done by monitoring the interaction force between a gold-coated AFM tip and a gold substrate, both presaturated by trisodium citrate. The addition of 4-MP was found to result in a remarkable change of tip−substrate adhesion force, which showed a gradual increase and finally reached a maximum. Using the chemical force titration technique, we estimated the surface pK1/2 of thus-formed 4-MP displacement film and compared with pure 4-MP self-assembled monolayer (SAM) formed on gold in ethanol solution. Our results indicate that the 4-MP molecules are more strongly adsorbed on gold than citrate anions, mostly via Au−S bonding, forming a less dense and mixed displacement film. The displacement adsorption kinetics seems very fast and it takes only ca. 2 min to establish more than 50% surface coverage of 4-MP molecules.
16 citations
TL;DR: In this paper, Er-doped BaTiO 3 films were deposited by the solgel method on SiO 2 /Si substrates and spontaneous luminescence in the films at 1.54 μm was observed under the excitation of both 514 and 980 nm lasers.
13 citations
TL;DR: It was found that the predominant emission at 549 nm has very different lifetimes upon excitation at 973 and 816 nm, which was explained by the mechanisms of excited state absorption (ESA) of individual Er3+ ion and cooperative energy transfer (CET) between two nearEr3+ ions for the up-conversion emission.
13 citations
TL;DR: In this paper, an up-conversion emission in violet (408 nm) from 93SiO2:7TiO 2:20AlO1.5 glasses synthesized by the sol-gel process was reported.
Journal Article•
TL;DR: MRI and fiberoptic pharyngoscopy are useful in locating the pharyngeal airway obstruction sites of OSAS patients and would be helpful in selecting treatment measures.
Abstract: OBJECTIVE To locate the obstruction sites in patients with obstructive sleep apnea syndrome (OSAS) during sleep by MRI imaging and dynamic fiberoptic pharyngoscopy. METHODS Fifteen OSAS patients confirmed by polysomnography (PSG) underwent ultrafast MR imaging during sleep. Their sequential midline sagittal and axial images were obtained and displayed in the cine mode. Then we examined the upper airway of the retropalate region (RP), retroglottal region (RG) and epiglottal region (EPG). We also did dynamic fiberoptic pharyngoscopy examination during sleep in 8 patients in another night. RESULTS Among the 15 patients, 3 had only RP region obstruction, 2 had only RG region obstruction, and the other 10 had both RP & RG airway obstruction. In the 8 cases monitored with both MRI and fiberoptic pharyngoscopy, the results obtained from the 2 methods were identical. CONCLUSION MRI and fiberoptic pharyngoscopy are useful in locating the pharyngeal airway obstruction sites of OSAS patients and would be helpful in selecting treatment measures.
Journal Article•
TL;DR: It is demonstrated that the persistence of early systemic and splanchnic hyperkinetic circulation after OLT may be the consequence of factors which maintain hyperhemodynamics in liver cirrhosis, where portal hypertension is not completely eliminated.
Abstract: OBJECTIVE To investigate early changes in systemic and splanchnic hemodynamics after orthotopic liver transplantation (OLT) in normal and cirrhotic rats METHODS Male Sprague-Dawley rats were divided into 4 groups: normal controls (NL, n = 10), intrahepatic portal hypertension (IHPH, n = 10) induced by injection of CCl4, normal rats with OLT (NL-OLT, n = 9) and IHPH rats with OLT (IHPH-OLT, n = 16) IHPH-OLT rats were divided into 2 subgroups: 3 days (Group A, n = 9) and 7 days (Group B, n = 7) after OLT OLT was performed in rats using cuffs for the anastomosis of the suprahepatic inferior vena cava, infrahepatic vena cava and portal vein Two weeks after production of IHPH rats, 7 days after NL-OLT rats, 3 days and 7 days after IHPH-OLT rats, radioactive microspheres were used in a hemodynamic study RESULTS There were no significant differences in hemodynamic changes between NL-OLT and NL rats, except mean arterial blood pressure (MAP) The characteristics of systemic and splanchnic hyperdynamic circulatory state, including increased cardiac output and splanchnic blood flow, decreased mean arterial blood pressure, total peripheral vascular resistance and splanchnic vascular resistance were observed in IHPH, IHPH-OLT A, and IHPH-OLT B rats The magnitude of hyperhemodynamics was in the order of IHPH > IHPH-OLT A > IHPH-OLT B rats Moreover, the derangement of splanchnic hyperhemodynamics was more significant than that of systemic hyperthermodynamics CONCLUSIONS The present study demonstrates that the persistence of early systemic and splanchnic hyperkinetic circulation after OLT may be the consequence of factors which maintain hyperhemodynamics in liver cirrhosis, where portal hypertension is not completely eliminated Hyperhemodynamics is not induced by OLT per se
Journal Article•
TL;DR: The study suggests that the pathogenesis of OSAS is related to the following factors: UA caliber and its AP/L ratio, the thickness of LW and PW, the size of LPFP in RP region, and the size and length of the palate.
Abstract: OBJECTIVE: To investigate the mechanisms of obstructive sleep apnea syndrome(OSAS) through observing the upper airway caliber and its corresponding pharyngeal wall of OSAS patients by MRI. METHODS: The upper airway(UA) of 18 OSAS patients were examined by MRI. The cross-sectional area of the UA and lateral parapharyngeal fat pad (LPFP) were calculated. The thickness of lateral and posterior pharyngeal wall (LW & PW) and other related indices were also measured. Nineteen nonsnoring age-matched normal subjects were selected as the control group. RESULTS: 1. The retropalatal (RP) and retroglossal (RG) region UA cross-sectional areas of OSAS patients were smaller than that of the control (P < 0.05). The epiglottal (EPC) region UA cross-sectional area was not significantly different between the 2 groups (P = 0.204). 2. The anterior-posterior/Lateral ratio(A-P/L) of UA in RP, RG, EPG regions was bigger in patients group than that of the control (P < 0.05). 3. The cross-sectional area of LPFP in patients group was larger than that of the control group (P = 1.76E-7). 4. The thickness of the PW in the RP, RG and EPG region was thicker in patients group than that of the control (P < 0.05). Although the thickness of the LW in the RP region was not statistically different between the 2 groups (P = 0.94), this index in RG and EPG region was larger in patients group than that of the control (P = < 0.05). 5. Sagittal MRI image showed that the length, thickness and cross-sectional area of the palate in patient group was larger than that of the control (P < 0.01). CONCLUSIONS: The study suggests that the pathogenesis of OSAS is related to the following factors: UA caliber and its AP/L ratio, the thickness of LW and PW, the size of LPFP in RP region, and the size and length of the palate.
Journal Article•
TL;DR: There was a significant difference between the Han and Uygur nationalities in the frequency distribution of VDR genotype (P < 0.01) and this investigation gave further evidence on the different etiopathology of osteoporosis in various ethnic groups.
Abstract: OBJECTIVE Polymorphism in vitamin D receptor (VDR) gene has been reported to play a major role in variations for genetic regulation of bone mass. Its role within various ethnic populations is not clear. The purpose of this study was to determine the frequencies of VDR genotypes in the Han and Uygur nationalities in China. METHODS We analyzed the polymorphism of Bsm I restriction enzyme by PCR-RFLP technique in 162 healthy postmenopausal women of the Han nationality and 50 healthy postmenopausal women of the Uygur nationality in China. The genotype frequencies of VDR were calculated using Hardy-Weinberg equilibrium formula. RESULTS In the Han nationality, the bb, Bb, and BB genotype accounted for 91.36%, 8.64% and 0%, respectively. In the Uygur nationality, frequencies were 74.00%, 18.00% and 8.00%, respectively. CONCLUSION There was a significant difference between the Han and Uygur nationalities in the frequency distribution of VDR genotype (P < 0.01). Compared with the Caucasian population in the United States, Australia and France, there was a similar value to Uygur nationality in the BB genotype. This investigation gave us further evidence on the different etiopathology of osteoporosis in various ethnic groups.
Journal Article•
TL;DR: A moniliformin(MON)-degrading bacterium strain was isolated from the mycotoxin-contaminated soil from Heilongjiang Province by the enrichment microculture technique, suggesting the existence of enzymes committed to MON degradation in the cell.
Abstract: A moniliformin(MON)-degrading bacterium strain, named as Y21-2, was isolated from the mycotoxin-contaminated soil from Heilongjiang Province by the enrichment microculture technique. This strain can grow with MON as its sole carbon and energy source. In the minimal medium with 500 micrograms/mL MON, the number of cells increased from 10(7) to 10(10). Traditional taxonomy, assays of its G + C content and 16S rDNA sequence homology identified Y21-2 as Rhizobiaceae, Ochrobactrum sp. Resting cell suspensions prepared from induced Y21-2 can degrade MON with great speed, which also suggested the existence of enzymes committed to MON degradation in the cell.
Journal Article•
TL;DR: In this article, chemical force microscopy (CFMMC) was used to measure the adhesion forces between Au coated Si 3N 4 tip and gold sample functionalized with NH 2 groups.
TL;DR: In this paper, a ferroelectric BaTiO3(001) ultrathin film (10 nm) was grown epitaxially on a substrate with laser molecular beam epitaxy (MBE).