Showing papers by "Nanchang University published in 2011"

Controllable Deposition of Platinum Nanoparticles on Graphene As an Electrocatalyst for Direct Methanol Fuel Cells

Abstract: Platinum nanoparticles (Pt NPs) with uniform size and high dispersion have been successfully assembled on poly(diallyldimethylammonium chloride) functionalized graphene oxide via a sodium borohydride reduction process. The loading concentration of Pt NPs on graphene can be adjusted in the range of 18–78 wt %. The obtained Pt/graphene nanocomposites are characterized by transmission electron microscopy, high resolution transmission electron microscopy, energy dispersive spectrometry, X-ray diffraction, and thermogravimetric analysis. The results show that the Pt NPs with sizes of approximate 4.6 nm uniformly disperse on graphene surface for all Pt loading densities. Electrochemical studies reveal that the Pt/graphene nanocomposites with electrochemically active surface area of 141.6 m2/g show excellent electrocatalytic activity toward methanol oxidation and oxygen reduction. The present method is promising for the synthesis of high performance catalysts for fuel cells, gas phase catalysis, and sensors.

Combination synchronization of three classic chaotic systems using active backstepping design.

Abstract: In this paper, an active backstepping design is proposed to achieve combination synchronization between three different chaotic systems: Lorenz system, Chen's system, and Lu system. The proposed method is a systematic design approach and consists in a recursive procedure that interlaces the choice of a Lyapunov function with the design of active control. Numerical simulations are shown to verify the feasibility and effectiveness of the proposed control technique.

Optimized ultrasonic-assisted extraction of flavonoids from Prunella vulgaris L. and evaluation of antioxidant activities in vitro

Abstract: The Box–Behnken design combined with response surface methodology was used to optimize ultrasonic-assisted extraction of total flavonoids from Prunella vulgaris L. The results indicated that the highest extraction yield of flavonoids by ultrasonic-assisted extraction could obtain to be 3.62% using ethanol concentration of 41% (v/v) as solvent and liquid to solid ratio of 30:1 (mL/g) for 30.5 min at the temperature of 79 °C. The crude extract was then purified by AB-8 macroporous adsorption resin, the flavonoids content in the purified extract increased to 81.58%. The antioxidant activities of the purified flavonoids were evaluated in vitro by scavenging capability of DPPH free radical and hydroxyl free radical, reducing power, total antioxidant capability and β-carotene bleaching test. The results showed that the flavonoids have significant antioxidant activities, which can be used as a source of potential antioxidant. Industrial Relevance The effective exploitation and application of the natural plant resources have very important significance for the industrial and economic development. Prunella vulgaris L. is a perennial plant commonly found in China and Europe, which was proved to be rich in flavonoids, triterpenes and phenolic acid. It has long been used as a folk medicine for alleviating sore throat, reducing fever and accelerating wound healing. Recent studies have demonstrated that the methanol or water extract of this herb exhibits many of the activities including antihyperglycemic activity, systemic anaphylaxis inhibition, antioxidative antiviral and antibacterial effects. However, attempts have not been made so far to investigate the ultrasonic-assistant extraction of flavonoids from P. vulgaris L. and evaluate their antioxidant activities in vitro. In this work, a four-variable, three-level experiment Box–Behnken design based on response surface methodology was used to optimize ultrasonic-assistant extraction of flavonoids from P. vulgaris L. The optimized results showed that the highest extraction yield of flavonoids by ultrasonic-assisted extraction could arrive 3.62%, using 41% (v/v) ethanol as solvent and 30:1 (mL/g) liquid to solid ratio for 30.5 min at the temperature of 79 °C. The suitability of the model equation for predicting the optimum response values was tested using the selected optimal conditions. The predicted extraction yield of flavonoids was 3.63%, which was consistent with the practical extraction yield of flavonoids of 3.62%. The crude extract was then purified by AB-8 macroporous adsorption resin, the flavonoids content in the purified extract increased to 81.58%. The antioxidant activities of the purified flavonoids were evaluated in vitro by scavenging capability of DPPH free radical and hydroxyl free radical, reducing power, total antioxidant capability and β-carotene bleaching test. The results indicated that the flavonoids have significant antioxidant activities, which can be used as a source of potential antioxidant or functional food material. We believe that the knowledge gained from this study should be helpful to further exploit and apply this resource .

Observations and simulations of non-local acceleration of electrons in magnetotail magnetic reconnection events

Abstract: Magnetic reconnection in magnetized plasmas represents a change in magnetic field topology and is associated with a concomitant energization of charged particles that results from a conversion of magnetic energy into particle energy. In Earth’s magnetosphere this process is associated with the entry of the solar wind into the magnetosphere and with the initiation of auroral substorms. Using data from the THEMIS mission, together with global and test particle simulations, we demonstrate that electrons are energized in two distinct regions: a low-energy population (less than or equal to a few kiloelectronvolts) that arises in a diffusion region where particles are demagnetized and the magnetic topology changes, and a high-energy component (approaching 100 keV) that results from betatron acceleration within dipolarization fronts that sweep towards the inner magnetosphere far from the diffusion region. Thus, the observed particle energization is associated with both magnetic reconnection and with betatron acceleration associated with macroscopic flows.

Molecular spectroscopic studies of farrerol interaction with calf thymus DNA.

Abstract: The interaction between farrerol and calf thymus DNA in a pH 7.4 Tris-HCl buffer was investigated with the use of neutral red (NR) dye as a spectral probe by UV–vis absorption, fluorescence, and ci...

Complementary and miscellaneous interventions for nocturnal enuresis in children

Abstract: Background Nocturnal enuresis (bedwetting) is a socially disruptive and stressful condition which affects around 15% to 20% of five year olds, and up to 2% of young adults. Objectives To assess the effects of complementary interventions and others such as surgery or diet on nocturnal enuresis in children, and to compare them with other interventions. Search methods We searched PubMed (1950 to June 2010), EMBASE (1980 to June 2010), the Traditional Chinese Medical Literature Analysis and Retrieval System (TCMLARS) (1984 to June 2010), Chinese Biomedical Literature Database (CBM) (1975 to June 2010), China National Knowledge Infrastructure (CNKI) (1979 to June 2010), VIP database (1989 to June 2010), and the reference lists of relevant articles, all last searched 26 June 2010. No language restriction was used. Selection criteria All randomised or quasi-randomised trials of complementary and other miscellaneous interventions for nocturnal enuresis in children were included except those focused solely on daytime wetting. Comparison interventions could include no treatment, placebo or sham treatment, alarms, simple behavioural treatment, desmopressin, imipramine and miscellaneous other drugs and interventions. Data collection and analysis Two reviewers independently assessed the quality of the eligible trials, and extracted data. Main results In 24 randomised controlled trials, 2334 children were studied, of whom 1283 received a complementary intervention. The quality of the trials was poor: 5 trials were quasi-randomised, 5 showed differences at baseline and 17 lacked follow up data. The outcome was better after hypnosis than imipramine in one trial (relative risk (RR) for failure or relapse after stopping treatment 0.42, 95% confidence interval (CI) 0.23 to 0.78). Psychotherapy appeared to be better in terms of fewer children failing or relapsing than both alarm (RR 0.28, 95% CI 0.09 to 0.85) and rewards (RR 0.29, 95%CI 0.09 to 0.90) but this depended on data from only one trial. Medicinal herbs had better results than desmopressin in one trial (RR for failure or relapse after stopping treatment 0.35, 95% CI 0.14 to 0.85). Acupuncture had better results than sham control acupuncture (RR for failure or relapse after stopping treatment 0.67, 95% CI 0.48 to 0.94) in a further trial. Active chiropractic adjustment had better results than sham adjustment (RR for failure to improve 0.76, 95% CI 0.60 to 0.95). However, each of these findings came from small single trials, and must be verified in further trials. The findings for diet and faradization were unreliable, and there were no trials including homeopathy or surgery. Authors' conclusions There was weak evidence to support the use of hypnosis, psychotherapy, acupuncture, chiropractic and medicinal herbs but it was provided in each case by single small trials, some of dubious methodological rigour. Robust randomised trials are required with efficacy, cost-effectiveness and adverse effects clearly reported.

Nanocomposite film based on graphene oxide for high performance flexible glucose biosensor

Abstract: A homogeneous chitosan–ferrocene/graphene oxide/glucose oxidase (CS–Fc/GO/GOx) nanocomposite film was successfully constructed as a novel platform for the fabrication of glucose biosensor. The morphologies and electrochemistry of the nanocomposite film were investigated by using scanning electron microscopy and electrochemical techniques including electrochemical impedance spectroscopy and cyclic voltammetry, respectively. Results demonstrated that the uniformly dispersed GO within the CS matrix could significantly improve the stability of GO and make it exhibit a positive charge, which was more favorable for the further immobilization of biomolecules, such as GOx, with higher loading. Further attaching redox mediator ferrocene group (Fc) to CS could not only effectively prevent the leakage of Fc from the matrix and retain its electrochemical activity, but also improve the electrical conductivity of CS and promote the electron-transfer between GOx and electrode. Biosensors based on this CS–Fc/GO/GOx film had advantages of fast response, excellent reproducibility, high stability, and showed a linear response to glucose in the concentration range from 0.02 to 6.78 mM with a detection limit of 7.6 μM at a signal-to-noise ratio of 3 and exhibited a higher sensitivity of 10 μA mM −1 cm −2 . The proposed strategy based on CS–Fc/GO nanocomposite for the immobilization of enzymes can be of practical relevance for the facile design of biosensors, as well as for the construction of new multifunctional bioelectrochemical systems.

Label-free colorimetric detection of trace cholesterol based on molecularly imprinted photonic hydrogels

Abstract: A novel colorimetric sensor for cholesterol assay was constructed by combining a molecular imprinting technique with photonic crystals. The molecularly imprinted photonic hydrogel (MIPH) film was prepared by a non-covalent, self-assembly approach using cholesterol as a template molecule, and exhibited a highly ordered three-dimensional macroporous structure characterized by scanning electron microscopy under the optimized imprinting conditions. Various factors affecting rebinding of cholesterol are discussed along with recognition specificity studies on its analogues of stigmasterol and ergosterol through estimation of UV-Vis and electrochemical impedance spectroscopy. The MIPH film generated a significantly readable optical signal directly self-reporting within less than 2 min upon binding cholesterol. The colorimetric measurement of cholesterol concentration strongly relies on the fact that the blue shift effect of the Bragg diffraction peak of the MIPH is gradually enlarged with the increase of cholesterol amounts. The detection level approached 10−13 g mL−1, which is comparable to that of fluorescence measurements. The simultaneous possession of high selectivity, high sensitivity, high stability, easy operation and being label-free enables this sensor to be potentially applicable for rapid on-site detection of trace cholesterol.

Highly sensitive humidity sensor based on amorphous Al2O3 nanotubes

Abstract: Amorphous Al2O3 nanotubes were obtained by the transformation of NH4Al(OH)2CO3 nanotubes annealed at 600 °C. The tube-like nanostructures not only increase efficient sites for gas adsorption, but also promote the dissociation of water absorbed onto the surfaces of the nanotube walls. Moreover, they also provide effective and fast channels for vapor and liquid transport. Therefore, the sensors based on Al2O3 nanotubes show high sensitivity and fast response/recovery time to humidity. The impedance changes approximately four orders of magnitude as relative humidity (RH) varies from 11% to 95% at the measured frequency of 40 Hz. Additionally, the sensor also presents relatively small hysteresis and long-term stability. For low RH levels, the protonic conductor is dominant, whereas for increasing RH levels the ionic contribution becomes prevalent. This study demonstrates that Al2O3 nanotubes have promising applications in environmental monitoring.

Strain engineering water transport in graphene nanochannels.

Abstract: Using equilibrium and nonequilibrium molecular dynamic simulations, we found that engineering the strain on the graphene planes forming a channel can drastically change the interfacial friction of water transport through it. There is a sixfold change of interfacial friction stress when the strain changes from -10% to 10%. Stretching the graphene walls increases the interfacial shear stress, while compressing the graphene walls reduces it. Detailed analysis of the molecular structure reveals the essential roles of the interfacial potential energy barrier and the structural commensurateness between the solid walls and the first water layer. Our results suggest that the strain engineering is an effective way of controlling the water transport inside nanochannels. The resulting quantitative relations between shear stress and slip velocity and the understanding of the molecular mechanisms will be invaluable in designing graphene nanochannel devices.

Low-level expression of let-7a in gastric cancer and its involvement in tumorigenesis by targeting RAB40C.

Abstract: Gastric cancer is the fourth most common cancer and the second leading cause of cancer mortality worldwide but the underlying molecular mechanism is not entirely clear. The objective of this study was to explore the role of let-7a microRNA (miRNA) in gastric tumorigenesis and the possible correlation between RAB40C and let-7a miRNA in gastric cancer. We found that expression of let-7a is reduced in human gastric cancer tissues and cell lines and there was a significant correlation between the level of let-7a expression and the stage of differentiation. Overexpression of let-7a resulted in a decrease in cell proliferation and G(1) arrest, significantly suppressed anchorage-dependent growth in vitro and the tumorigenicity of gastric cancer cells in a nude mouse xenograft model. Furthermore, we demonstrated that RAB40C is regulated directly by let-7a and plays an essential role as a mediator of the biological effects of let-7a in gastric tumorigenesis. This study revealed that let-7a is significant in suppressing gastric cancer growth in vivo and in vitro and provided the first evidence that RAB40C is negatively regulated by let-7a at the posttranscriptional level via binding to the 3'-untranslated region of RAB40C messenger RNA in gastric cancer. The results of this study suggest that let-7a and RAB40C are potentially useful targets for gastric cancer diagnosis and therapy.

Understanding Plant-Microbe Interactions for Phytoremediation of Petroleum-Polluted Soil

Abstract: Plant-microbe interactions are considered to be important processes determining the efficiency of phytoremediation of petroleum pollution, however relatively little is known about how these interactions are influenced by petroleum pollution. In this experimental study using a microcosm approach, we examined how plant ecophysiological traits, soil nutrients and microbial activities were influenced by petroleum pollution in Phragmites australis, a phytoremediating species. Generally, petroleum pollution reduced plant performance, especially at early stages of plant growth. Petroleum had negative effects on the net accumulation of inorganic nitrogen from its organic forms (net nitrogen mineralization (NNM)) most likely by decreasing the inorganic nitrogen available to the plants in petroleum-polluted soils. However, abundant dissolved organic nitrogen (DON) was found in petroleum-polluted soil. In order to overcome initial deficiency of inorganic nitrogen, plants by dint of high colonization of arbuscular mycorrhizal fungi might absorb some DON for their growth in petroleum-polluted soils. In addition, through using a real-time polymerase chain reaction method, we quantified hydrocarbon-degrading bacterial traits based on their catabolic genes (i.e. alkB (alkane monooxygenase), nah (naphthalene dioxygenase) and tol (xylene monooxygenase) genes). This enumeration of target genes suggests that different hydrocarbon-degrading bacteria experienced different dynamic changes during phytoremediation and a greater abundance of alkB was detected during vegetative growth stages. Because phytoremediation of different components of petroleum is performed by different hydrocarbon-degrading bacteria, plants’ ability of phytoremediating different components might therefore vary during the plant life cycle. Phytoremediation might be most effective during the vegetative growth stages as greater abundances of hydrocarbon-degrading bacteria containing alkB and tol genes were observed at these stages. The information provided by this study enhances our understanding of the effects of petroleum pollution on plant-microbe interactions and the roles of these interactions in the phytoremediation of petroleum-polluted soil.

Dietary L-arginine supplementation enhances intestinal development and expression of vascular endothelial growth factor in weanling piglets.

Abstract: Oral administration of L-arginine has been reported to prevent gut disease in human infants. However, little is known about the effects of dietary arginine supplementation on intestinal development of weaned piglets. In the present study, twenty 21-d-old castrated piglets with 5·3 (SEM 0·13) kg body weight (BW) were weaned from sows, individually housed and randomly assigned to one of the two maize- and soyabean meal-based diets supplemented with 0 or 1% L-arginine. After consuming the diets for 7 d, six pigs were randomly selected from each group to obtain various tissues. Compared with control pigs, dietary supplementation with 1% L-arginine did not affect feed intake but enhanced (P<0·05) the relative weight of the small intestine (+33 %), daily BW gain (+38 %) and feed efficiency (+28 %). The villus height of the duodenum, jejunum and ileum in arginine-supplemented piglets was 21, 28 and 25% greater (P<0·05) than in the nonsupplemented control group. Arginine supplementation increased (P<0·05) protein levels for vascular endothelial growth factor(VEGF) in duodenal, jejunal and ileal mucosae by 14, 39 and 35 %, respectively. Compared with the control group, dietary supplementation with 1% L-arginine increased (P<0·05) plasma concentrations of arginine and insulin (+36 %), and decreased (P<0·05) plasma concentrations of cortisol (233 %), NH3 (221 %) and urea (219 %). These results indicate that arginine supplementation enhances intestinal growth, development and expression of VEGF in early-weaned pigs fed a maize- and soyabean meal-based diet. The findings may have important implications for neonatal pigs under stressful or diseased conditions.

Rapid detection of melamine with 4-mercaptopyridine-modified gold nanoparticles by surface-enhanced Raman scattering.

Abstract: A surface-enhanced Raman scattering (SERS) strategy based on 4-mercaptopyridine (MPY)-modified gold nanoparticles (AuNPs) was developed for the rapid and sensitive detection of melamine in milk powder. The SERS measurement of melamine strongly relied on the "hotspot" effect, in which AuNPs immediately aggregated upon the addition of melamine, leading to significantly enhanced Raman intensity of the reporter molecule MPY and a color change for the solution from red to blue-gray. The limit of detection based on a signal to noise of 3 (S/N = 3) was found to be as low as 0.1 ppb of melamine, with an excellent linearity of 0.5-100 ppb, demonstrating a higher sensitivity and a wider quantitation range than direct SERS sensing methods based on enhanced substrate. An impressive specificity for melamine detection over various common metal ions and excipients in dairy products, even at concentrations of 100-fold higher than melamine, was achieved. Good recoveries of 88.5% and 111.7% were obtained from milk samples spiked to 20 and 100 ppb levels, respectively. The proposed method is potentially applicable for the rapid in situ determination of melamine in complex matrices. .

Atmospheric deposition and leaching of nitrogen in Chinese forest ecosystems

Abstract: Data have been compiled from published sources on nitrogen (N) fluxes in precipitation, throughfall, and leaching from 69 forest ecosystems at 50 sites throughout China, to examine at a national level: (1) N input in precipitation and throughfall, (2) how precipitation N changes after the interaction with canopy, and (3) whether N leaching increases with increasing N deposition and, if so, to what extent. The deposition of dissolved inorganic N (DIN) in precipitation ranged from 2.6 to 48.2 kg N ha−1 year−1, with an average of 16.6 kg N ha−1 year−1. Ammonium was the dominant form of N at most sites, accounting for, on average, 63% of total inorganic N deposition. Nitrate accounted for the remaining 37%. On average, DIN fluxes increased through forest canopies, by 40% and 34% in broad-leaved and coniferous forests, respectively. No significant difference in throughfall DIN inputs was found between the two forest types. Overall, 22% of the throughfall DIN input was leached from forest ecosystems in China, which is lower than the 50–59% observed for European forests. Simple calculations indicate that Chinese forests have great potential to absorb carbon dioxide from the atmosphere, because of the large forest area and high N deposition.

Adsorption and aggregation behavior of tetrasiloxane-tailed surfactants containing oligo(ethylene oxide) methyl ether and a sugar moiety.

Abstract: Three novel amphiphilic dicephalic (double-headed) surfactants containing oligo(ethylene-oxide)methyl-ether and a sugar moiety TGA-m (m = 1, 2, and 3) that incorporate a tetrasiloxane at the terminus of a hydrocarbon chain were designed and synthesized. Their surface activity and aggregation behavior in aqueous solution were systematically investigated by surface tension, dynamic light scattering (DLS), and transmission electron microscopy (TEM) techniques at 298 K. The surface tension measurements provided the critical aggregation concentration (CAC) and the surface tension at the CAC (γcac). In addition, with application of the Gibbs adsorption isotherm, the maximum surface excess concentration (Γmax) and the minimum surface area/molecule (Amin) at the air−water interface were estimated. The effect of EO chain length on the surface activity and aggregation behavior was also investigated. It was found that both the γcac and the CAC were lower than those for reported traditional hydrocarbon surfactants. A...

Competitive binding of small molecules with biopolymers: a fluorescence spectroscopy and chemometrics study of the interaction of aspirin and ibuprofen with BSA.

Abstract: The interaction of aspirin and ibuprofen with bovine serum albumin (BSA) was studied by spectrofluorimetry under simulated physiological conditions. Both aspirin and ibuprofen quenched the intrinsic fluorescence of BSA and the binding ratios obtained were 2 : 1 for aspirin-BSA and 3 : 1 for ibuprofen-BSA interactions, respectively. The thermodynamic parameters (ΔH, ΔS and ΔG) obtained from the fluorescence spectroscopy data showed that the binding of aspirin to BSA involved van der Waals interactions and hydrogen bonds. Competitive experiments using warfarin and diazepam as site markers indicated that aspirin was mainly located in the hydrophobic pocket of site II of the protein as well as to a small extent in site I. Furthermore, the competitive interaction of the aspirin and ibuprofen with BSA, which was studied with the use of the three-way excitation-emission fluorescence spectra and a parallel factor analysis (PARAFAC) chemometrics method, showed that the competitive effect of ibuprofen was stronger than that of aspirin, i.e. the former molecule replaced the aspirin from the aspirin-BSA complex.

Antioxidant activity and free radical-scavenging capacity of Gynura divaricata leaf extracts at different temperatures.

Abstract: Background: Extraction temperature influences the total phenolic content (TPC), total flavonoid content (TFC) of medicinal plant extracts to a great extend. TPC and TFC are the principle activity constituents present in the plant. The effects of extraction temperature on TPC, TFC and free radical-scavenging capacity of Gynura divaricata leaf extracts are worth to study. Materials and Methods: Folin-Ciocalteu and aluminum chloride colorimetric assay were used to determine the TPC and TFC of Gynura divaricata leaf extracts at different temperatures. The antioxidant and free radical-scavenging activity were measured by 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid (ABTS) and phosphomolybdenum methods. Results: TPC and TFC were significantly elevated with increasing extraction temperature (from 40°C to 100°C). However, TPC and TFC were not significantly different (P > 0.05) at the extraction temperatures 90°C and 100°C. Also, the extracts obtained at a higher temperature exhibited a significant free radical-scavenging activity compared with extraction at lower temperatures ( P R 2 = 0.9229), ABTS ( R 2 = 0.9951) free radical-scavenging capacity, and total antioxidant activity ( R 2 = 0.9872) evaluated by phosphomolybdenum method. Conclusion: The TPC and TFC of G. divaricata leaf was significantly influenced by the extraction temperatures, which were the main antioxidant constituents present in the G. divaricata plant.