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Biomedical subjects

Bing Tan

Publications and source records attributed to Bing Tan.

12 recordsLinked to original sources
PubMed2006

Study of the effects of progressive changes in alkoxysilane structure on sol-gel reactivity.

Effects of the structure of an alkoxysilane on the early reaction kinetics of sol-gel polymerization are investigated in basic and acidic conditions. Six silanes, including tetraethoxysilane (TEOS), tetramethoxysilane (TMOS), methyltrimethoxysilane (MTMS), bis(trimethoxysilyl)ethane (BTMSE), bis(trimethoxysilyl)hexane (BTMSH), and bis(trimethoxysilylpropyl)amine (BTMSPA), are selected to examine the effects of progressive changes in the silane's structure. In basic conditions, reactivities of the silanes follow the pairwise trends TEOS << TMOS, TMOS > MTMS, MTMS < BTMSE, BTMSE >> BTMSH, and BTMSH << BTMSPA. Hydrolysis rate coefficients of BTMSE, TMOS, MTMS, and BTMSPA are similar in value and are almost one order of magnitude larger than the coefficients of BTMSH and TEOS. In acidic conditions, the pairwise reactivity trends are TEOS approximately TMOS, TMOS < MTMS, MTMS > BTMSE, BTMSE >> BTMSH, and BTMSH > BTMSPA. The condensation rate coefficients of BTMSH and BTMPA are much smaller than the others. Theses relationships can be explained mainly on the basis of the expected inductive and steric factors of the silanes. Bulky organics attached to the silane lead to low reactivity in both acidic and basic conditions. A high electron density at silicon leads to a low reactivity in basic conditions but a high reactivity in acidic conditions (pH approximately 2.3). Only BTMSPA in basic conditions defies these trends, possibly because of the effects of solvation near the reactive silicon site.

Journal Article↗
PubMed2006

Freestanding mesoporous quasi-single-crystalline CO3O4 nanowire arrays.

We report a facile template-free method for the large-area growth of freestanding hollow Co3O4 nanowire arrays on a variety of substrates including transparent conducting glass, Si wafer, and copper foil, et al. These nanowires have the interesting combined properties of mesoporosity and quasi-single-crystallinity. With their high surface area and crystallinity, and their direct growth on conductive substrate, these Co3O4 nanowire arrays will have promising applications in lithium-ion batteries, chemical sensing, and field-emission and electrochromic devices. Using the prepared nanowire arrays as electrode, an electrochemical sensor for hydrogen peroxide sensing has been demonstrated.

Journal Article↗
PubMed2006

Facial nerve function in carcinoma of the parotid gland.

AIM: To analyse, for patients with carcinoma of the parotid gland, the prognostic value for treatment outcome of the function of the facial nerve (NVII), and determining facial nerve dysfunction after treatment. METHODS AND MATERIALS: In a retrospective study of the Dutch head and Neck cooperative group (NWHHT), data of 324 patients with parotid carcinoma were analysed. The function of N VII before treatment was intact in 77%, partially and completely impaired in 14% and 7%, respectively. Eighty-eight percent of the patients were treated surgically, and 77% of them were treated by a combination of postoperative radiotherapy. In 21% NVII was sacrificed, a reconstruction was performed in one of three. RESULTS: Independent risk factors for N VII dysfunction before treatment were tumour localisation, positive neck nodes at presentation, pain, increasing age, and perineural invasion. Regional, not local, control was significantly impaired for complete facial paralysis. N VII dysfunction was an independent factor for disease free survival, and was 69%, 37% and 13% for normal, partially and completely impaired function, respectively. After treatment 22% of the patients experienced a partial paralysis, and 13% of the patients experienced a complete paralysis of N VII. CONCLUSION: For patients with parotid carcinoma, facial nerve function before treatment is a strong prognostic factor for disease free survival.

Adolescent↗
PubMed2006

Dye-sensitized solar cells based on anatase TiO2 nanoparticle/nanowire composites.

Dye-sensitized solar cells were fabricated based on the composites of anatase TiO2 nanoparticles and single crystalline anatase TiO2 nanowires. Nanoparticle/nanowire composites can possess the advantages of both building blocks, i.e., the high surface area of nanoparticle aggregates and the rapid electron transport rate and the light scattering effect of single-crystalline nanowires. Three different composites were prepared with 5 wt %, 20 wt %, and 77 wt % nanowires, respectively. The performances of composite solar cells were compared with pure nanoparticle cells at a series of film thickness. With low nanowire concentrations (5 wt % and 20 wt %), the composite films maintain similar specific surface area as the pure nanoparticle films, while the composite cells show higher short-circuit current density and open-circuit voltage. An enhancement of power efficiency from 6.7% for pure nanoparticle cells to 8.6% for the composite cell with 20 wt % nanowires has been achieved under 1 Sun AM1.5 illumination (100 mW/cm2). For the composite film with 77 wt % nanowires, the nanowires became the major phase. Their less compact packing resulted in significant decrease of the specific surface area, and thus the current density. However, with the increase of film thickness, the current density showed a continuous increase in the whole thickness range up to 17 microm, indicating the improved electron diffusion length due to the formed nanowire network. The nanowires also helped to preserve crack-free thick films. These results show that employing nanoparticle/nanowire composites represents a promising approach for further improving the efficiencies of sensitized solar cells.

Journal Article↗
PubMed2005

Unusual dependence of particle architecture on surfactant concentration in partially fluorinated decylpyridinium templated silica.

A series of porous silica particles is prepared with different concentrations of the fluorinated cationic surfactant 1-(3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10)-heptadecafluorodecyl)pyridinium chloride (HFDePC) to trace the changes in pore structure and particle morphology as the surfactant concentration increases. At the lowest concentration studied (1.5 mmol/L), the product consists of small round particles with close-packed cylindrical mesopores. As the HFDePC concentration increases, macroporous voids are introduced to create multi-chambered hollow particles with mesoporous walls. With a still higher concentration of HFDePC the macropore volume decreases, and elongated, tactoid-like nanoparticles are formed with random mesh-phase pores oriented with silica layers perpendicular to the main axis of the particles. Further increasing the concentration of HFDePC eventually leads to the formation of round particles with disordered pores. These changes are consistent with increasing HFDePC concentration favoring increasingly oblate or disklike micelles. The process of forming the elongated particles with random mesh-phase structure is investigated by TEM of chilled and dried samples. The results indicate that the oriented tactoid-like structure forms spontaneously within 2 min by co-assembly of silica and HFDePC rather than by preferred growth perpendicular to the layers. The particle shape and layer orientation are consistent with what would be expected for a liquid-crystal particle with orientation-dependent surface tension. Finally, we compare samples prepared with a high HFDePC and with good or poor mixing. With inadequate mixing, a gel layer forms at the top of the sample which is composed of elongated mesoporous particles with a thick coating of microporous silica. The lower particulate phase contains small disordered particles similar to those obtained in a well-mixed sample. Presumably, the structure of the upper layer results from initial immiscibility of the precursor and slow diffusion of silicates out of the gel.

Journal Article↗
PubMed2005

Anti-hepatoma effect of arsenic trioxide on experimental liver cancer induced by 2-acetamidofluorene in rats.

AIM: To study the anti-hepatoma efficiency of arsenic trioxide (As(2)O(3)) in the treatment of experimental rat hepatocellular carcinoma (HCC) induced by 2-acetamidofluorene (2-FAA) and to elucidate the possible mechanisms. METHODS: SD rats (2 mo old) had been fed with 2-FAA for 8 wk to induce HCC, and then they were treated with As(2)O(3) or matrine. On d 29, the rats were killed and the liver was weighed and liver tumors were counted. The histological changes of liver tissue were observed under microscope, and the cellular dynamic parameters were studied by flow cytometry. Immunohistochemistry (two-step method) was used to observe the expression of vascular endothelial growth factor (VEGF) and micro-vessel density (MVD) on consecutive sections. The pathological parameters were also analyzed, the levels of serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), total bilirubin (TBi), and direct bilirubin (DBi). RESULTS: The number of liver tumors decreased significantly in groups treated with As(2)O(3), especially in medium-dose (1 mg/kg) group (t = 2.80, P<0.01). As(2)O(3) caused HCC cell death via apoptosis; necrosis was seen and apoptosis was common when the dose was 1 mg/kg. Proliferation index decreased sharply in medium-dose (1 mg/kg) group (7.87+/-4.11 vs 24.46+/-6.49, t = 2087, P<0.01), but not in 0.2 mg/kg group. However, S-phase fraction decreased dramatically in both groups, it reached the bottom level only when the dose was 1 mg/kg compared with control (0.40+/-0.13 vs 3.01+/-0.51, t = 2.97, P<0.01), and it was obviously accompanied with accumulation of cells in G(0)/G(1) (G(0)/G(1) restriction). The expressions of VEGF and MVD in medium-dose (1 mg/kg) group were significantly lower than normal saline group (0.63+/-0.74 vs 2.44+/-0.88, P<0.05; 15.75+/-3.99 vs 47.44+/-13.41, t = 2.80, P<0.01). Compared with normal saline group, medium- and low-dose groups As(2)O(3) and matrine lowered the levels of ALT in serum (61.46+/-9.46, 63.75+/-20.40, 61.18+/-13.00 vs 108.98+/-29.86, t = 2.14, P<0.05), but had no effect on the level of serum AST, TBi, and DBi. CONCLUSION: As(2)O(3) had inhibitory effect on growth of experimental HCC in rats induced by 2-FAA, but had no obvious effect on normal hepatic cells. The mechanisms may involve decrease of cell division, accumulation of cells in G(0)/G(1) phase, apoptosis of tumor cells, and inhibitory effect on angiogenesis through blocking VEGF.

2-Acetylaminofluorene↗
PubMed2005

Dual latex/surfactant templating of hollow spherical silica particles with ordered mesoporous shells.

Hollow spherical silica particles with hexagonally ordered mesoporous shells are synthesized with the dual use of cetyltrimethylammonium bromide (CTAB) and unmodified polystyrene latex microspheres as templates in concentrated aqueous ammonia. In most of the hollow mesoporous particles, cylindrical pores run parallel to the hollow core due to interactions of CTAB/silica aggregates with the latices. Effects on the product structure of the CTAB:latex ratio, the amount of aqueous ammonia, and the latex size are studied. Hollow particles with hexagonally patterned mesoporous shells are obtained at moderate CTAB:latex ratios. Too little CTAB causes silica shell growth without surfactant templating, and too much induces nucleation of new mesoporous silica particles without latex cores. The concentration of ammonia must be large to induce co-assembly of CTAB, silica, and latex into dispersed particles. The results are consistent with the formation of particles by addition of CTAB/silica aggregates to the surface of latex microspheres. When the size and number density of the latex microspheres are changed, the size of the hollow core and the shell thickness can be controlled. However, if the microspheres are too small (50 nm in this case), agglomerated particles with many hollow voids are obtained, most likely due to colloidal instability.

Journal Article↗
PubMed2004

Hyplip2, a new gene for combined hyperlipidemia and increased atherosclerosis.

OBJECTIVE: We previously reported the mapping of a quantitative trait locus (QTL) on chromosome 15 contributing to hyperlipidemia in a cross between inbred strains MRL/MpJ (MRL) and BALB/cJ (BALB). Using marker-assisted breeding, we constructed a congenic strain in which chromosome 15 interval from MRL is placed on the genetic background of BALB. The congenic allowed us to confirm the QTL result and to further characterize the properties and location of the underlying gene. METHODS AND RESULTS: On chow and high-fat (atherogenic) diets, the congenic mice exhibited higher levels of plasma triglycerides and cholesterol than BALB mice. In response to the atherogenic diet, the congenic mice but not BALB mice exhibited a dramatic approximately 30-fold increase in atherogenic lesions accompanied by approximately 2-fold decrease in high-density lipoprotein cholesterol levels. With respect to atherosclerotic lesions and some lipid parameters, this chromosome 15 gene, designated Hyplip2, exhibited dominant inheritance. Expression array analyses suggested that Hyplip2 may influence inflammatory and bile acid synthesis pathways. Finally, we demonstrated the usefulness of subcongenic strains to narrow the locus (50 Mbp) with the goal of positionally cloning Hyplip2. CONCLUSIONS: Our data demonstrate that the Hyplip2 gene significantly contributes to combined hyperlipidemia and increased atherosclerosis in mice.

Animals↗
PubMed2004

Elongated silica nanoparticles with a mesh phase mesopore structure by fluorosurfactant templating.

Mesoporous silica materials with pore structures such as 2D hexagonal close packed, bicontinuous cubic, lamellar, sponge, wormhole-like, and rectangular have been made by using surfactant templating sol-gel processes. However, there are still some "intermediate" phases, in particular mesh phases, that are formed by surfactants but which have not been made into analogous silica pore structures. Here, we describe the one-step synthesis of mesoporous silica with a mesh phase pore structure. The cationic fluorinated surfactant 1,1,2,2-tetrahydroperfluorodecylpyridinium chloride (HFDePC) is used as the template. Like many fluorinated surfactants, HFDePC forms intermediate phases in water (including a mesh phase) over a wider range of compositions than do hydrocarbon surfactants. The materials produced by this technique are novel elongated particles in which the layers of the mesh phase are oriented orthogonal to the main axis of the particles.

Journal Article↗
PubMed2003

[Development of MOIMS on environmental data distribution].

'Environmental WebGIS system for Ganjiang Watershed', based on 1:250,000 topographic spatial database and environmental database of Jiangxi province, was developed. In the system, a hybrid strategy was adopted. And the GIS analysis functions of MapObjects and Map server functions of MOIMS were integrated in the system. Users can use GIS functions, such as zooming in, zooming out, panning, making theme maps, finding geographic objects by environmental attribute values etc., through web browser on the client computers. With the application of the WebGIS system, expanding the GIS users' range, making the GIS operation easily, and assistanting environmental management and decision can be completed.

Environmental Health↗
PubMed2002

Truncation mutations in ABCA1 suppress normal upregulation of full-length ABCA1 by 9-cis-retinoic acid and 22-R-hydroxycholesterol.

Mutations in ABCA1 uniformly decrease plasma HDL-cholesterol (HDL-C) and reduce cholesterol efflux, yet different mutations in ABCA1 result in different phenotypic effects in heterozygotes. For example, truncation mutations result in significantly lower HDL-C and apoliprotein A-I (apoA-I) levels in heterozygotes compared with nontruncation mutations, suggesting that truncation mutations may negatively affect the wild-type allele. To specifically test this hypothesis, we examined ABCA1 protein expression in response to 9-cis-retinoic acid (9-cis-RA) and 22-R-hydroxycholesterol (22-R-OH-Chol) in a collection of human fibroblasts representing eight different mutations and observed that truncation mutations blunted the response to oxysterol stimulation and dominantly suppressed induction of the remaining full-length allele to 5-10% of wild-type levels. mRNA levels between truncation and nontruncation mutations were comparable, suggesting that ABCA1 expression was suppressed at the protein level. Dominant negative activity of truncated ABCA1 was recapitulated in an in vitro model using transfected Cos-7 cells. Our results suggest that the severe reduction of HDL-C in patients with truncation mutations may be at least partly explained by dominant negative suppression of expression and activity of the remaining full-length ABCA1 allele. These data suggest that ABCA1 requires a physical association with itself or other molecules for normal function and has important pharmacogenetic implications for individuals with truncation mutations.

ATP Binding Cassette Transporter 1↗