L. Cheng

Sichuan University, Hua-yang, Sichuan, China

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Publications (28)43.43 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Employing a novel Ba-rich Nd2Ba4Cu2O9 (Nd242) phase in the precursor, air-processed NdBCO bulk superconductors were grown by using NdBCO film seeds. To obtain single-phase Nd242 powders, the sintering conditions were adjusted by varying the processing atmosphere and temperature. Furthermore, the influences of adding Nd242 on both the superconducting property and the crystal growth of the NdBCO bulk were investigated. We present experimental evidence suggesting that the addition of Nd242 can effectively improve the superconducting performance of NdBCO bulks, which showed optimal properties when the Ba:Cu ratio in the precursor was 0.80. We also found that the addition of Nd242 caused an increase in growth rate, particularly along the c-axis direction of the NdBCO. Moreover, the effect of the addition of Nd242 on the growth rate was clarified.
    Superconductor Science and Technology 07/2014; 27(8):085016. · 2.76 Impact Factor
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    ABSTRACT: Objective: Dental resin composites are increasingly used for tooth cavity restorations due to their esthetics and direct-filling capabilities. However, composites tend to accumulate more biofilms in vivo, and biofilm acids contribute to secondary caries and restoration failure. Therefore, the objectives of this study were to synthesize new quaternary ammonium methacrylates (QAMs) with different alkyl chain lengths (CL) to formulate antibacterial nanocomposites, and investigate the effects of CL on mechanical and antibacterial properties of nanocomposites. Method: A series of QAMs with different CL was synthesized. Five different alkyl organo-halides were chosen to react with dimethylamino methacrylate, resulting in new antibacterial monomers DMAPM (CL=3), DMAHM (CL=6), DMADDM (CL=12), DMAHDM (CL=16) and AMAODM (CL=18). Each QAM was incorporated into a nanocomposite containing 20% of nanoparticles of amorphous calcium phosphate (NACP) for remineralization. This yielded five nanocomposites with the five new QAMs. Two composites without QAM served as control. A flexural test was used to measure the mechanical properties. A dental plaque microcosm biofilm model was used to evaluate antibacterial activity. Result: Flexural strength (mean±sd; n=6) of nanocmposites with QAMs was (68±7)MPa, similar to (70±6)MPa of control composites (p>0.1). Composites with QAMs were strongly-antibacterial. Increasing CL from 3 to 16 enhanced the antibacterial activity (p<0.05), and decreased the CFU by 2 orders of magnitude. Further increasing the CL to 18 decreased the antibacterial potency. At CL=16, the metabolic activity and lactic acid production of adherent biofilms were 10-fold lower than those on control composites. Conclusion: New antibacterial monomers were synthesized and incorporated into NACP nanocomposites to combine antibacterial and remineralization capabilities. Increasing CL from 3 to 16 decreased the CFU by 2 orders of magnitude. The new QAM-NACP nanocomposite possessed potent anti-biofilm activity without compromising load-bearing properties, and is promising for antibacterial and remineralizing restorations to inhibit caries.
    IADR General Session and Exhibition 2014; 06/2014
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    ABSTRACT: Objective: Rho is important in the migration of dental pulp cells (DPCs). Rho-associated kinase (ROCK) and mammalian homolog of Drosophila diaphanous 1 (mDia1) are two major effectors of RhoA. However, the relationships between these factors remain unknown. We investigated the effects of mDia1 and ROCK on the behavior of DPCs under two different conditions—low and high levels of GTP–RhoA (activated RhoA). Method: Lysophosphatidic acid (LPA) was used to activate RhoA signaling pathway, and the function of mDia1 and ROCK were inhibited by short interfering RNA and the specific inhibitor Y-27632, respectively. The migration of DPCs was detected by transwell migration and scratch-wound assay. Cytoskeleton and focal adhesions were investigated with immunofluorescent methods by confocal laser scanning microscopy. Cell adhesion and spreading were analyzed by adhesion and spreading assays. The phosphorylations of focal adhesion kinase (FAK) and paxillin were detected by Western blotting. Result: Under normal culture conditions with low-level GTP–RhoA, inhibition of mDia1 and ROCK increased cell migration. Inhibition of ROCK, but not mDia1, dramatically changed cell morphology and cytoskeleton structure. Silence of mDia1 increased cell adhesion and the phosphorylations of FAK and paxillin. When RhoA was activated by LPA, ROCK inhibition still increased cell speed while inhibition of mDia1 decreased cell migration. Inhibition of mDia1 or ROCK suppressed LPA-induced cytoskeleton remodeling. However, inhibition of each alone increased cell adhesion and spreading. Conclusion: It might be concluded that mDia1 and ROCK have dual effects on the migration and adhesion of DPCs. Under the conditions with low-level GTP–RhoA, mDia1 and ROCK limited the cell migration rate. ROCK might be involved in the maintenance of cell morphology and cytoskeleton. Under the conditions with high-level GTP–RhoA, mDia1 promoted cell migration. mDia1 and ROCK might be involved in the reorganization of cell cytoskeleton.
    IADR General Session and Exhibition 2014; 06/2014
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    ABSTRACT: Using liquid-phase epitaxy, a novel approach is reported for preparing a pure a-axis-oriented YBa2Cu3Oy film (a-film) on a (110) NdGaO3 substrate in ambient air, which is hard to achieve through conventional processes since its formation requires an extremely low supersaturation state. In the new process, instead of commonly used growth processes in a metastable zone, a-films were grown in an unstable zone of the Y–Ba–Cu–O solution. Under that circumstance, a homogeneous nucleation catastrophe occurred in the solution, leading to instantaneous consumption of most of the supersaturated Y solute. Thus a high degree of supersaturation rapidly relaxed to an ultra-low level. By controlling either the cooling rate or the growth temperature, a wide window for the formation of the a-film was gained. In principle, this new method should be universally valid for more crystal or film growth processes, particularly when an ultra-low supersaturation is required in solution.
    Journal of Applied Crystallography 12/2013; 46(6). · 3.34 Impact Factor
  • L. CHENG, K. ZHANG, X. ZHOU, H. XU
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    ABSTRACT: Objective: Dental resin composites have been increasingly used as direct fillings due to their excellent esthetics and rapidly improving performance. However, composites accumulate more biofilms/plaques than other restoratives.Two main challenges facing composite restorations are secondary caries and bulk fracture. The objectives of this study were to: (1) develop a novel nanocomposite containing nanoparticles of amorphous calcium phosphate (NACP), quaternary ammonium dimethacrylate (QADM) and silver nanoparticles; and (2) investigate their mechanical and antibacterial durability. Method: A spray-drying technique yielded NACP with particle size of 116 nm. The nanocomposite contained NACP and reinforcement glass fillers, with QADM and NAg in the resin. Three nanocomposites were thus made: (1) NanoACP+QADM composite, (2) NanoACP+NAg composite, and (3) NanoACP+QADM+NAg composite. A commercial composite without fluoride was tested as controls. Specimens were immersed in distilled water at 37ºC for 1day, 3 months, 6 months, 9 months and 12 months. Composites were inoculated with saliva microcosm. Biofilm viability, metabolic activity, and lactic acid production were measured. Result: After 12 months water-aging, NACP nanocomposite containing QADM and NAg had flexural strength and elastic modulus matching those of commercial controls (p>0.1). Incorporation of QADM or NAg into NACP nanocomposite greatly reduced microcosm biofilm viability, metabolic activity, CFU and acid production. Adding the QADM and NAg together in the same composite resulted in a stronger antibacterial capability than using the QADM or NAg alone.(p<0.05). Their anti-biofilm activity was maintained after 12 months of water-aging. Conclusion: The novel NACP-QADM nanocomposite greatly decreased microcosm biofilms, while matching the load-bearing capability of commercial composites without antibacterial properties. The NACP-QADM nanocomposite with strong and durable antibacterial properties, together with its Ca-PO4 release capability previously-reported, may render it useful for caries-inhibiting restorations.
    IADR Asia/Pacific Region (APR) Regional Meeting and Co-Annual Scientific Meeting of IADR Divisions 2013; 08/2013
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    ABSTRACT: Applying a cost-effective process with a simple one-side-heating furnace, two layers of YBa2Cu3Ox (YBCO) bulks were successfully grown in one batch by using NdBa2Cu3Ox (NdBCO) thin-film-seeds deposited on MgO substrates. Due to the large temperature difference between the two layers, the seed-induced growth began at the bottom layer much later than that at the top layer. Remarkably, NdBCO films on the bottom layer samples survived a long time (over 15 h) above the growth temperature and effectively induced the YBCO growth. The significant thermal stability of the films, i.e., the tolerance for a long holding time on the surface of the molten pellet, is supposed to relate to a competition between the dissolution/diffusion of film materials into the liquid and NdBCO grain coarsening/Nd-YBCO crystallization.
    Journal of Applied Physics 05/2013; 113(20). · 2.21 Impact Factor
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    ABSTRACT: Dental materials with anticaries properties could help inhibit the development of lesions. Objectives: To investigate the antibacterial effects in vitro of incorporating nanoparticles of silver (NAg) and nanoparticles of amorphous calcium phosphate (NACP) into a bonding agent, and to assess the effects of NACP-filled nanocomposite on enamel mineral loss in an in situ model. Methods: For the in vitro study, commercial adhesive and primer were used as control. NAg were incorporated into the primer and adhesive at 0.1% by mass. NACP were mixed into adhesive at 10%, 20%, 30% and 40%. Dentin bond strength and oral microcosm biofilm response were measured. For the in situ study, caries-like lesions were produced in which 25 volunteers wore palatal devices with enamel slabs restored using NACP nanocomposite or control composite. Ca and P ion concentrations were measured in biofilms on the slabs. Enamel demineralization was assessed by transverse microradiography. Results: Bonding agents containing NAg and NACP showed bond strengths ranged from 26 to 34 MPa, with no significant difference (p>0.1). Substantial reductions in bacterial viability were obtained (p<0.05), including metabolic activity (reduced by 60%), CFU for total microorganisms, total streptococci, and mutans streptococci (50-85%), and lactic acid production (65-85%). SEM examination showed NACP infiltration into dentinal tubules. In the in situ study, NACP nanocomposite significantly increased Ca and P ion concentrations in biofilms and substantially reduced mineral loss in enamel (p<0.05). Conclusions: Incorporation of NACP and NAg imparted a great anticaries effect by inhibiting the cariogenic biofilm viability and lactic acid production, as well as promoting remineralization in tooth enamel. The method of combining an antibacterial agent and a remineralizing agent in the adhesive or the composite is promising to inhibit secondary caries, and may have potential for use in a wide range of materials including adhesives, composites, cements, and sealants.
    IADR/AADR/CADR General Session and Exhibition 2013; 03/2013
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    ABSTRACT: Composites are the principal material for tooth cavity restorations due to their esthetics and direct-filling capabilities. However, composites accumulate biofilms in vivo, and secondary caries due to biofilm acids is the main cause of restoration failure. Objectives: (1) Synthesize new antibacterial monomers and (2) Develop nanocomposite containing nanoparticles of amorphous calcium phosphate (NACP) and new antibacterial monomer. Methods: Two new antibacterial monomers were synthesized: dimethylaminohexyl methacrylate (DMAHM) with a carbon chain length of 6, and dimethylaminododecyl methacrylate (DMADM) with a chain length of 12. A spray-drying technique was used to make NACP. DMADM was incorporated into NACP nanocomposite at mass fractions of 0%, 0.75%, 1.5%, 2.25% and 3%. A dental plaque microcosm biofilm model with human saliva as inoculum measured the viability, metabolic activity, and lactic acid production of biofilms on composites. Results: Minimum inhibitory concentration (MIC) and bactericidal concentration (MBC) measurements indicated that DMAHM was more potent than quaternary ammonium dimethacrylate (QADM). MIC and MBC of DMADM were 2-3 orders of magnitude lower than those of DMAHM, and approached those of chlorhexidine control. At each DMADM mass fraction, DMADM-NACP nanocomposites had strengths similar to that of composite control (69±8)MPa (p>0.1). With 3% DMADM in NACP nanocomposite, the metabolic activity of adherent biofilms was (0.11±0.02), which represents a 95% reduction compared to composite control (p<0.05). Lactic acid production by biofilms on NACP nanocomposite containing 3% DMADM was (0.22±0.08)mmol/L, which represents a 99% reduction compared to composite control (p<0.05). Biofilm colony-forming units on NACP nanocomposite with 3% DMADM were reduced by 2-3 orders of magnitude (p<0.05). Conclusions: New antibacterial monomers were synthesized, and the carbon chain length had a strong effect on antibacterial efficacy. The new DMADM-NACP nanocomposite possessed potent anti-biofilm activity without compromising load-bearing properties, and is promising for antibacterial and remineralizing dental restorations to inhibit secondary caries.
    IADR/AADR/CADR General Session and Exhibition 2013; 03/2013
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    ABSTRACT: Gd–Ba–Cu–O (GdBCO) bulk superconductors of diameter of 42 mm have been fabricated via a multi-seeded melt growth (MSMG) method in air using well-oriented Nd–Ba–Cu–O thin film seeds. The effect of seed orientation on the growth process and the formation of grain boundaries were investigated systematically by using two thin film seeds arranged with crystallographic orientations of (100)/(100) and (110)/(110), respectively. The multi-seeded process was then firstly extended to four thin film seeds arranged asymmetrically [(110)/(110)], which involved placing the seeds in pairs, with two adjacent seeds positioned relatively close to each other and the other two at a greater separation. This modified technique is beneficial to obtain a large size GdBCO bulk in a shorter time as well as clean grain boundaries by rejecting the excess melt liquid thoroughly along the growth front. More interestingly, a domain of non-equilibrium shape is formed during the MSMG process, which leads potentially to the growth of much larger samples. The growth mode of the enhancement in growth rate is interpreted by the presence of a high index crystallographic (110) face to the initial growth front.
    Journal of Crystal Growth 03/2013; 366:1–7. · 1.55 Impact Factor
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    ABSTRACT: By employing YBCO/LAO thin films as seeds, we succeeded in growing REBa2Cu3Ox (REBCO, RE=Y, Sm) thick films via the LPE method in air. Remarkably, a completely covered YBCO thick film with the c-axis orientation was achieved. Moreover, SmBCO LPE films were effectively induced by the YBCO/LAO thin films at a processing temperature of 1055 °C, indicating that the YBCO/LAO thin film possesses a superheating property. Compared with the YBCO/MgO thin film, the YBCO/LAO thin film has a potentially higher thermal stability in LPE, due to its better lattice fitness at the film/substrate interface. On the other hand, compared to the thick films induced by NdGaO3 (NGO) substrates, YBCO/LAO thin-film-seeded thick films have the broad average spacing of about 150 μm between adjacent cracks, almost five times wider than the former, which benefits the practical application in electronic devices. In short, the YBCO/LAO thin film becomes a third promising candidate for inducing REBCO LPE thick films, combined with conventionally used YBCO/MgO thin films and single-crystal NGO substrates.
    Journal of Crystal Growth 03/2013; 366:47–50. · 1.55 Impact Factor
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    ABSTRACT: In this work, we report a strengthened superheating effect caused by a buffering YBa2Cu3Oy (YBCO or Y123) layer in the Nd1+x Ba2−x Cu3O7−y (NdBCO or Nd123) thin film with MgO substrate (i.e., NdBCO/YBCO/MgO thin film). In the cold-seeding melt-textured (MT) growth, the NdBCO/YBCO/MgO film presented an even higher superheating level, about 20 °C higher than that of nonbuffered NdBCO film (i.e., NdBCO/MgO film). Pole figure (X-ray Φ-scan) measurement reveals that the NdBCO/YBCO/MgO film has better in-plane alignment than the NdBCO/MgO film, which may be the main origin of the enhanced thermal stability. Using this NdBCO/YBCO/MgO film as the seed and under a maximum processing temperature (T max) up to 1120 °C, we succeeded in growing various RE1+x Ba2−x Cu3O7−y (REBCO, RE=Gd, Sm, Nd, RE refers to rare elements) bulk superconductors and recycling the failed REBCO (RE=Y) bulks in a simple and feasible process.
    Journal of Superconductivity and Novel Magnetism 01/2013; 26(4). · 0.93 Impact Factor
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    ABSTRACT: Current challenges in restorative dentistry include secondary caries especially at the tooth-restoration margins. An antibacterial and remineralizing adhesive system would be beneficial in inhibiting caries. Objectives: (1) Incorporate nanoparticles of silver (NAg) and quaternary ammonium dimethacrylate (QADM) as antibacterial agents, and nanoparticles of amorphous calcium phosphate (NACP) as remineralizing agent, into to an adhesive system; and (2) investigate the effects on dentin bond strength and dental plaque microcosm biofilm response. Methods: An experimental adhesive system was prepared. Primer = PMGDM/HEMA (3.3/1 ratio) + 1% BAPO + 50% acetone (all mass%). Adhesive = BisGMA/TEGMA (7/3 ratio) + 1% BAPO). PMGDM: pyromellitic glycerol dimethacrylate. BAPO: phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide. HEMA: 2-hydroxyethyl methacrylate. The NAg were incorporated into the primer and adhesive at 0.1%. QADM (10%) and NACP (10%, 20%, 30% and 40%) were mixed into the adhesive. A human saliva microcosm biofilm model was used on disks with primer covering the adhesive on the top of a composite. Biofilm metabolic activity, colony-forming unit counts, lactic acid production and bond strength were measured. ANOVA and Tukey tests (α=5%) were used. Results: Incorporation of NAg, QADM and NACP did not alter the human dentin shear bond strength (31 to 39 MPa; p>0.1). Statistically significant reductions (p<0.05) were found in total microorganisms, total streptococci, and mutans streptococci in groups containing NAg, QADM and NACP, compared to the control. Significant reductions were also achieved in biofilm viability and lactic acid production via NAg and QADM, compared to the control. Conclusions: The incorporation of antibacterial agents NAg and QADM as well as remineralizing agent NACP into the bonding system did not compromise the bond strength, while greatly reducing the microcosm biofilm viability and lactic acid production. The concept of a nanotechnology approach for achieving antibacterial and remineralizing capabilities may have a wide applicability to other dental bonding agents.
    06/2012
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    ABSTRACT: REBa2Cu3Oy (RE123 or REBCO, RE = rare earth elements) bulk high-temperature superconductors have a potential perspective for large-scale engineering applications. However, the cost of REBCO bulk production is rather high, considering high failure rates, expensive RE materials, and Pt or Ag addition. Using the cold-seeding in the top-seeded melt growth, a simple and feasible process, we succeeded in recycling the failed REBCO (RE = Y) bulks. The distinctive feature of this recycling process is the use of YBCO-buffered NdBCO films as seeds, which have high thermal stability and can endure a maximum processing temperature (Tmax) up to 1120 °C to enable full decomposition of solid REBCO. Three typical microstructures were recognized in the failed samples attributed to the inherent differences in the non-optimized growth heating profiles. Preferential recycling procedures were chosen according to the difficulty of the failed-samples decomposition, which has a certain connection with the microstructures of the failed bulks. Finally, after oxygenation, the recycled bulks demonstrate good superconducting properties.
    Journal of Applied Physics 05/2012; 111(10). · 2.21 Impact Factor
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    ABSTRACT: Antibacterial bonding agents could combat recurrent caries at the tooth-composite margins. The objectives of this study were to develop novel antibacterial dentin primers containing quaternary ammonium dimethacrylate (QADM) and nanoparticles of silver (NAg), and to investigate the effects on dentin bond strength and dental plaque microcosm biofilms for the first time. Scotchbond Multi-Purpose ("SBMP") bonding agent was used. QADM and NAg were incorporated into SBMP primer, yielding 4 primers: SBMP primer (control), control + 10% QADM (mass), control + 0.05% NAg, and control + 10% QADM + 0.05% NAg. Human saliva was collected to grow microcosm biofilms. The NAg particle size (mean ± SD; n = 100) was 2.7 ± 0.6 nm. Dentin shear bond strengths (n = 10) with human third molars were approximately 30 MPa for all groups (p > 0.1). QADM-NAg-containing primer increased the bacteria inhibition zone by 9-fold, compared with control primer (p < 0.05). QADM-NAg-containing primer reduced lactic acid production and colony-forming units of total micro-organisms, total streptococci, and mutans streptococci by an order of magnitude. In conclusion, novel QADM-NAg-containing primers were strongly antibacterial without compromising dentin bond strength, and hence are promising to inhibit biofilms and secondary caries. The processing method of incorporating QADM and NAg together into the same primer produced the strongest antibacterial effect, which could have a wide applicability to other bonding systems.
    Journal of dental research 04/2012; 91(6):598-604. · 3.46 Impact Factor
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    ABSTRACT: Objectives: To develop an antibacterial and remineralizing nanocomposite by incorporating quaternary ammonium dimethacrylate (QADM) and silver nanoparticles (NanoAg) into amorphous calcium phosphate nanocomposite (NanoACP). Methods: QADM was bis(2-methacryloyloxyethyl) dimethylammonium bromide (ionic dimethacrylate-1). It was synthesized from 2-(N,N-dimethylamino)ethyl methacrylate and 2-bromoethyl methacrylate. NanoAg was synthesized by dissolving Ag 2-ethylhexanoate salt in 2-(tert-butylamino)ethyl methacrylate. Three antibacterial nanocomposites were developed: NanoACP+QADM; NanoACP+NanoAg; NanoACP+QADM+NanoAg. Composite disks were inoculated with Streptococcus mutans. Biofilm viability, metabolic activity, and lactic acid production were measured. Results: Flexural strength of NanoACP+QADM (53±7 MPa), NanoACP+NanoAg (67±4 MPa), and NanoACP+QADM+NanoAg (54±12 MPa) matched those of commercial control composites (Helimolar: 57±12 MPa; Renamel: 56±8 MPa) (p>0.1). Colony-forming unit (CFU) counts (x106) of biofilms on NanoACP+QADM+NanoAg was (8±1), significantly lower than (120±11) on Helimolar, and (130±11) on Renamel (p<0.05). NanoACP+QADM+NanoAg had lower CFU counts than NanoACP+QADM (55±7) and NanoACP+NanoAg (31±6) (p<0.05). MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay showed that NanoACP+QADM+NanoAg significantly (p<0.05) reduced the metabolic activity of biofilms to (1.4±0.2 A540/cm2), compared to (2.2±0.1 A540/cm2) for Helimolar, and (2.7±0.3 A540/cm2) for Renamel. Lactic acid production of biofilms on NanoACP+QADM+NanoAg was (6.4±0.4 mmol/L), significantly (p<0.05) less than those on commercial composites (Helimolar: 13.2±0.8 mmol/L; Renamel: 16.7±0.6 mmol/L). Lactic acid on NanoACP+QADM+NanoAg (6.4±0.4 mmol/L) was significantly (p<0.05) less than NanoACP+QADM (8.2±0.9 mmol/L) and NanoACP+NanoAg (7.3±0.7 mmol/L) (p<0.05). Therefore, combining QADM with NanoAg into the same composite rendered it more strongly antibacterial than either QADM or NanoAg alone. Conclusions: The novel NanoACP+QADM+NanoAg nanocomposite was strongly-antibacterial and greatly reduced the CFU counts, metabolic activity, and lactic acid production of S. mutans biofilms, while possessing mechanical properties similar to commercial composites. This nanocomposite is promising to have the double benefits of remineralization and antibacterial capabilities to inhibit dental caries. Supported by NIH R01 DE17974 and DE14190 (HX), and NIDCR-NIST Interagency Agreement Y1-DE-7005-01.
    03/2012
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    ABSTRACT: Secondary caries is a frequent reason for restoration failure, resulting from acidogenic bacteria and their biofilms. The objectives of this study were to: (1) develop a novel nanocomposite containing nanoparticles of amorphous calcium phosphate (NACP) and quaternary ammonium dimethacrylate (QADM); and (2) investigate its mechanical and antibacterial durability. A spray-drying technique yielded NACP with particle size of 116 nm. The nanocomposite contained NACP and reinforcement glass fillers, with QADM in the resin. Two commercial composites were tested as controls. Composites were inoculated with Streptococcus mutans. After 180-day water-aging, NACP+QADM nanocomposite had flexural strength and elastic modulus matching those of commercial controls (p > 0.1). NACP+QADM nanocomposite reduced the biofilm colony-forming units (CFU) by 3-fold, compared with commercial composites (p < 0.05). Metabolic activity and lactic acid production of biofilms on NACP+QADM were much less than those on commercial composites (p < 0.05). The antibacterial properties of NACP+QADM were maintained after water-aging for 30, 90, and 180 d (p > 0.05). In conclusion, the novel NACP-QADM nanocomposite greatly decreased biofilm metabolic activity, CFU, and lactic acid, while matching the load-bearing capability of commercial composites without antibacterial properties. The NACP-QADM nanocomposite with strong and durable antibacterial properties, together with its previously reported Ca-PO(4) release capability, may render it useful for caries-inhibiting restorations.
    Journal of dental research 03/2012; 91(5):460-6. · 3.46 Impact Factor
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    ABSTRACT: In this work, we report a strengthened superheating effect caused by a buffering YBa2Cu3Oy (Y123 or YBCO) layer in the Nd1+xBa2-xCu3O7-y (Nd123 or NdBCO) thin film with MgO substrate (i.e., NdBCO/YBCO/MgO thin film). In the cold-seeding melt-textured (MT) growth, the NdBCO/YBCO/MgO film presented an even higher superheating level, about 20 {\deg}C higher than that of non-buffered NdBCO film (i.e., NdBCO/MgO film). Using this NdBCO/YBCO/MgO film as seeds and undergoing a maximum processing temperature (Tmax) up to 1120 {\deg}C, we succeeded in growing various RE1+xBa2-xCu3O7-y (REBCO, RE=rare elements) bulk superconductors, including Gd1+xBa2-xCu3O7-y (GdBCO), Sm1+xBa2-xCu3O7-y (SmBCO) and NdBCO that have high peritectic temperatures (Tp). The pole figure (X-Ray \phi-scan) measurement reveals that the NdBCO/YBCO/MgO film has better in-plane alignment than the NdBCO/MgO film, indicating that the induced intermediate layer improves the crystallinity of the NdBCO film, which could be the main origin of the enhanced thermal stability. In short, possessing higher thermal stability and enduring a higher Tmax in the MT process, the NdBCO/YBCO/MgO film is beneficial to the growth of bulk superconductors in two aspects: (1) broad application for high-Tp REBCO materials; (2) effective suppression against heterogeneous nucleation, which is of great assistance in growing large and high-performance REBCO crystals.
    Superconductor Science and Technology 10/2011; 25(3). · 2.76 Impact Factor
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    ABSTRACT: The effect of oxygen partial pressure on the thermal stability of Nd-123 superconductor thin films was investigated by means of high temperature in situ microscopy. It was found that the thermal stability of Nd-123 films decreases as the oxygen partial pressure increases. We attribute the thermal stability suppression to the increased growth rate of Nd-422 and a high concentration difference ratio. Under the assumption of quasi-equilibrium, a simplified model for peritectic melting of RE-123 was suggested.
    Journal of Applied Physics 08/2011; 110(4). · 2.21 Impact Factor
  • S B Yan, L J Sun, T Y Li, L Cheng, X Yao
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    ABSTRACT: Following the increasing interest in the high thermal stability of REBa2Cu3O7 − x (RE-123, RE = rare earth) thin films as seed materials, thermal stabilities of Y-123 and Nd-123 thin films were investigated by two methods: high temperature in situ microscopy and the melt growth process. A monotonic dependence of thermal stability on RE solubility in the Ba–Cu–O liquid was observed. The thermal stability of RE-123 films was found to strongly depend on the melting growth process, which is predominated by the melting rate of the RE-123 phase. Under the assumption of quasi-equilibrium, a simplified model of solute transport was suggested. The correlation between the solute inflow and outflow indicates that the melting rate of RE-123 is proportional to the growth rate of the RE2BaCuO5 (RE-211) phase and the ratio of the concentration difference between the RE-211 growth front and the RE-123 melting border. We conclude that an Nd-123 thin film is more unstable than a Y-123 thin film because of the higher melting rate, resulting from a higher growth rate of the RE-211 phase and a higher concentration difference ratio.
    Superconductor Science and Technology 05/2011; 24(7):075007. · 2.76 Impact Factor
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    ABSTRACT: To investigate the effects of lysophosphatidic acid (LPA) and the Rho/Rho-associated kinase (ROCK) pathway on adhesion of dental pulp cells (DPCs). Human DPCs were cultured ex vivo. After treatment of LPA and Y-27632, a specific ROCK inhibitor, changes in focal contacts (FCs) were examined by immunofluorescent staining. Activation of FCs proteins was examined by measuring tyrosine 397 phosphorylation of focal adhesion kinase (FAK) and paxillin using immunoblotting. The data were analysed by Student's t-test. The immunofluorescent staining indicated LPA stimulation induced larger focal adhesion in the cell periphery, compared with the control. Inhibition of ROCK by Y-27632 decreased the formation of FCs markedly, even in the LPA-stimulated cells. LPA also increased the level of tyrosine phosphorylation of paxillin at 30min (P<0.05) and FAK at 5 and 30min (P<0.05). Furthermore, p-paxillin levels declined immediately after Y-27632 treatment and remained low at 5, 30, 60min. Y-27632 also suppressed the effects of LPA on p-paxillin and p-FAK at 5 and 30min (P<0.05). LPA activated Rho and then subsequently activated ROCK, suggesting that LPA influences the FCs of DPCs by modulating tyrosine phosphorylation of FAK and paxillin via the Rho/ROCK pathway.
    International Endodontic Journal 11/2010; 44(1):2-8. · 2.05 Impact Factor

Publication Stats

66 Citations
43.43 Total Impact Points

Institutions

  • 2010–2014
    • Sichuan University
      • • State Key Laboratory of Oral Diseases
      • • West China School of Stomatology
      Hua-yang, Sichuan, China
  • 2009–2014
    • Shanghai Jiao Tong University
      • • State Key Laboratory of Metal Matrix Composites
      • • Department of Physics
      Shanghai, Shanghai Shi, China
  • 2012–2013
    • University of Maryland, Baltimore
      • Department of Endodontics, Prosthodontics and Operative Dentistry
      Baltimore, Maryland, United States