scispace - formally typeset
Search or ask a question

Showing papers by "Feng Zhang published in 1998"


Journal ArticleDOI
TL;DR: A three-dimensional model of the pRNA hexamer is presented and it is shown that this capacity of pRNA to form higher multimers by intermolecular base pairing of identical subunits represents a new RNA structural motif.

158 citations


Journal ArticleDOI
TL;DR: Genetic variation in DRD1 and DRD3 genes may act to modify the course of AD, predisposing to the development of psychotic or aggressive symptoms.
Abstract: Objective: To examine if selected polymorphisms in the dopamine receptor genes DRD1, DRD2, DRD3, and DRD4 are associated with the presence of psychosis or aggressive behavior in patients with Alzheimer disease (AD) Design: A cohort of patients with AD were longitudinally evaluated for behavioral symptoms and classified with regard to the presence of psychotic symptoms and physical aggression

142 citations


Journal ArticleDOI
TL;DR: In vivo investigation of low-temperature isotropic pyrolytic carbon (LTI carbon) cylinders, widely used to fabricate artificial heart valves, and titanium-oxide-coated LTI carbon cylinders with diameters of 5 mm and thicknesses of 0.5 mm showed that the amount of thrombus on the Titanium oxide films was much less than that formed on the surface of LTIcarbon alone.
Abstract: Titanium oxide films were synthesized by ion-beam-enhanced deposition. The films were prepared by depositing titanium atoms and simultaneously bombarding them with Xe+ ions at an energy of 40 keV in an O2 environment. An in vivo investigation, which entailed implanting low-temperature isotropic pyrolytic carbon (LTI carbon) cylinders, widely used to fabricate artificial heart valves, and titanium-oxide-coated LTI carbon cylinders with diameters of 5 mm and thicknesses of 0.5 mm into the ventral aorta of dogs for 14 days, showed that the amount of thrombus on the titanium-oxide-coated LTI carbon was much less than that formed on the surface of LTI carbon alone. Scanning electron microscopy (SEM) was used to observe the morphology of thrombus. On the titanium oxide films no platelet aggregation was found, almost no red blood cells were damaged, and almost no fibrin was found on the surface. However, all three characteristics were found on the surface of LTI carbon alone, proving that the blood compatibility of titanium oxide films is better than that of LTI carbon and titanium-oxide-coated LTI carbon. © 1998 John Wiley & Sons, Inc. J. Biomed Mater Res, 42, 128–133, 1998.

77 citations


Journal ArticleDOI
TL;DR: In this paper, a change from (002) to (101) preferred orientation of titanium oxide films with rutile type structure was observed with increasing O 2 pressure from 4 × 10 −2 to 2×10 −1 Pa.

47 citations


Journal ArticleDOI
TL;DR: In this article, X-ray photoelectron spectroscopy (XPS), Rutherford backscattering spectroscopic (RBS) and Xray diffraction (XRD) were used to characterize the deposited titanium oxide films.
Abstract: Titanium oxide films were prepared by ion beam assisted deposition on an Eaton Z-200 system, in which the deposition of titanium evaporated from an electron beam evaporator and the bombardment with xenon ions at an energy of 40 keV extracted from an arc discharge-type ion source proceeded simultaneously in an O2 environment. X-ray photoelectron spectroscopy (XPS), Rutherford backscattering spectroscopy (RBS) and X-ray diffraction (XRD) were used to characterize the deposited films. It was found that the atomic ratio of O/Ti is about 1.85:1. XPS analysis shows that Ti2+, Ti3+ and Ti4+ chemical states exist on the titanium oxide films. The films deposited are in principle crystalline TiO2 with a rutile structure. The films exhibit a highly (100) orientation and increase the degree of (100) orientation with ion beam current density decreasing. The blood compatibility of titanium oxide films was studied by in vitro and in vivo investigation. In vitro investigation includes clotting time measurement and platelet adhesion. Clotting time measurements show that the clotting time of titanium oxide films is longer than that of low temperature isotropic pyrolytic carbon (LTI-carbon), which is widely used as artificial heart valves in clinics. There are also fewer platelets adhered to and deformed on the titanium oxide films compared to the LTI-carbon. In vivo investigation, implanting LTI-carbon and titanium oxide coated LTI-carbon into the ventral aorta of a dog for two weeks, shows that the amount of thrombus on titanium oxide coated LTI-carbon is only about 1/8 compared to that of LTI-carbon. The relationship between chemical states and blood compatibility was discussed. We think that the existence of Ti2+ and Ti3+ is beneficial for blood compatibility.

42 citations


Journal ArticleDOI
TL;DR: RNA aptamers, ligands best suited for prohead binding, were obtained by multiple rounds of in vitro selection and essentially recapitulated the natural evolution of pRNA.

30 citations


Journal ArticleDOI
TL;DR: In this article, the influence of ion bombardment during deposition on the texture of titanium dioxide films was studied and a change of preferred orientation from (110) to (200) with increase of ion to deposited atom arrival ratio was observed in case Ne+ and Xe+ ion bombardment were used during film growth.
Abstract: Rutile-type titanium dioxide films, which exhibits tetragonal structure, were synthesized by ion beam assisted deposition with ion beam incidence inclined 45° to the substrate. The influence of ion bombardment during deposition on the texture of films was studied. A change of preferred orientation from (110) to (200) with increase of ion to deposited atom arrival ratio was observed in case Ne+ and Xe+ ion bombardment were used during film growth, respectively. It is found that in rutile type TiO2 films (110) plane exhibits the lowest surface free energy and crystallites with (100) orientation have the widest channel to ions when ion beam injects with direction 45° to the film. The preferred orientation of titanium oxide films from (110) to (200) is accounted for in terms of channeling of ions and surface free energy. When arrival ratio of ion to atom is low, crystallites with (110) orientation which has lowest surface free energy grow preferentially. As the increase of arrival ratio, the damage induced by...

28 citations


Journal ArticleDOI
Feng Zhang1, Zhihong Zheng1, Yu Chen1, Yingjun Mao1, Xianghuai Liu1 
TL;DR: In this paper, the effect of the xenon ion beam bombardment on the structure of the films prepared by electron beam evaporation on a titanium oxide thin layer (500A) which has been deposited during ion bombardment was studied.

12 citations


Journal ArticleDOI
TL;DR: The results show that the blood compatibility of rutile-type titanium oxide fi is better than that of low temperature isotropic pyrolytic carbon (LTI-carbon), which is widely used to fabricate artificial heart valve.
Abstract: Titanium oxide films were synthesized by ion beam enhanced deposition, where the films were prepared by depositing titanium atoms and simultaneously bombarding with Xe+ ions at an energy of 40 keV in an O2 environment. The titanium oxide films exhibit rutile-type structure with (100) orientation and the O/Ti ratio is about 2:1. Ti2+, Ti3+ and Ti4+ coexist in the films.In vitro andin vivo investigations were used to investigate the blood compatibility of titanium oxide films. The results show that the blood compatibility of rutile-type titanium oxide fi is better than that of low temperature isotropic pyrolytic carbon (LTI-carbon), which is widely used to fabricate artificial heart valve. It is thought that rutile-type titanium oxide coated LTI-carbon most probably becomes new biomaterial to fabricate artificial heart valves.

11 citations


Journal Article
TL;DR: The close association of the hotspot mutation of p53 gene in Qidong HCC with the presence of HBVx gene sequence suggests that such mutation is the molecular footprint of the combined effect of aflatoxin B1 exposure and HBVX gene product.
Abstract: Objective Hepatitis B virus (HBV) is a major etiological agent of hepatocellular carcinoma (HCC). The x gene of HBV genome (HBVx) is considered as its oncogene. In order to assess the extent of its involvement in hepatocarcinogenesis, both HBsAg sero-positive and mainly sero-negative HCC were searched for the presence, expression and mutation status of the x gene of HBV, as well as its association with 249 codon hot spot mutation of p53 gene. Methods Using PCR, RT-PCR, PCR-RFLP and DNA sequencing, studies were more focused on 25 HBsAg sero-negative, pathologically diagnosed HCC patients operated during 1991 to 1996 mainly in Qidong and also in Beijing. Results The x gene sequence of HBV was found by PCR without exception in all 25 seronegative HCC DNA (100% 25/25) and also in all 19 seropositive counterparts. The RNA messages of HBVx gene were found in all 8 HCC patients randomly selected from the seronegative group. Sequence analysis of the HBVx gene showed the presence of missense mutation in the 130 and 131 codon in 4 of 6 samples studied. Using PCR-RFLP, missense mutation of the 249 codon was identified in 57% (12/21) of all HBsAg negative cases from Qidong. No such mutations were found in the 4 Beijing counterparts. Conclusion HBVx gene sequence was universally present in HBsAg negative HCC samples of Qidog studied, indicating the important role of HBVx gene in hepatocarcinogenesis of the high incidence area. The close association of the hotspot mutation of p53 gene in Qidong HCC with the presence of HBVx gene sequence suggests that such mutation is the molecular footprint of the combined effect of aflatoxin B1 exposure and HBVx gene product.

10 citations


Journal ArticleDOI
TL;DR: In this paper, it has been found that the roughness of the TiO 2 -Si film is larger than that of the film without ion bombardment, and a small fraction of Ti 2 O 3 in the corundum structure is found to coexist with Ti 2 grains.
Abstract: Titanium oxide films prepared on Si(1 0 0) by Xe + ion beam bombardment during deposition were characterized by atomic force microscopy (AFM) and transmission electron microscopy (TEM). It has been found that the film is very dense and the roughness is larger than that of the film without ion bombardment. There is a Ti–O and Si–O amorphous layer at the TiO 2 –Si interface formed by Xe + bombardment. TiO 2 and Si exist following orientation relationship: (1 0 0) TiO 2 //(2 0 0)Si, (0 1 1)TiO 2 //(0-22)Si and [0-11]TiO 2 //[0 1 1]Si. A small fraction of Ti 2 O 3 in the corundum structure is found to coexist with TiO 2 grains.

Journal ArticleDOI
TL;DR: In this paper, the surface free energy and ion channeling effects of all the films were studied in terms of X-ray diffraction and Raman spectroscopy, and the structural characteristics of all films were analyzed by using the Raman spectrum.
Abstract: In this article, titanium dioxide films prepared by neon ion beam assisted deposition (IBAD) in an oxygen environment were investigated. The deposition rate was varied from 0.2 to 0.4 nm/s while the current density and ion energy were kept at 20 μA/cm 2 and 40 keV. The structural characteristics of all films were studied by X-ray diffraction and Raman spectroscopy. Results show that all the films exhibit a rutile phase. The location of (2 0 0) diffraction peaks deviated from the standard value. Simultaneously, the relative intensity of (2 0 0)/(1 1 0) peaks decreases with increasing evaporation rate. All results are discussed in terms of surface free energy and ion channeling effects.

Proceedings ArticleDOI
22 Jun 1998
TL;DR: Titanium oxide films were prepared by ion beam assisted deposition (IBAD), where the films were synthesized by depositing titanium atoms and simultaneously bombarding with an Xe/sup +/ ion beam at an energy of 40 keV in an O/sub 2/ environment as mentioned in this paper.
Abstract: Titanium oxide films were prepared by ion beam assisted deposition (IBAD), where the films were synthesized by depositing titanium atoms and simultaneously bombarding with an Xe/sup +/ ion beam at an energy of 40 keV in an O/sub 2/ environment. The results show that titanium oxide films exhibit rutile type structure with [100] orientation. The surface energy of titanium oxide and titanium films prepared by IBAD were measured by the contact angle method. The results show that titanium oxide films with [100] orientation exhibit surface energy with dispersion component, /spl alpha/=5.79 (dyne/cm)/sup 1/2/ and polar component, /spl beta/=2.94 (dyne/cm)/sup 1/2/. The protein adsorption properties on low temperature isotropic pyrolytic carbon (LTI-carbon) and titanium oxide films with [100] orientation were studied by the radioisotope labeling method. The results show that there are less human fibrinogen (HFG) adsorbed on the surface of titanium oxide films between adsorbed HFG and proteins in solutions. In HSA/HFG (human fibrinogen) binary system, less HFG is adsorbed on titanium oxide films. The relationship between adsorption and surface energy was discussed. It can be concluded that the titanium oxide films with [100] orientation are better than those of LTI-carbon from a blood compatibility point of view.