Showing papers by "Donghua University published in 2010"
TL;DR: In this article, a facial aqueous solution was used to extract fully exfoliated graphene nanosheets and polyvinyl alcohol (PVA) for the preparation of polymer nanocomposites.
Abstract: Graphene, flat carbon nanosheets, has generated huge activity in many areas of science and engineering due to its unprecedented physical and chemical properties. With the development of wide-scale applicability including facile synthesis and high yield, this exciting material is ready for its practical application in the preparation of polymer nanocomposites. Here we report that nanocomposites based on fully exfoliated graphene nanosheets and poly(vinyl alcohol) (PVA) are prepared via a facial aqueous solution. A significant enhancement of mechanical properties of the graphene/PVA composites is obtained at low graphene loading; that is, a 150% improvement of tensile strength and a nearly 10 times increase of Young’s modulus are achieved at a graphene loading of 1.8 vol %. The comparison between the experimental results and theoretical simulation for Young’s modulus indicates that the graphene nanosheets in polymer matrix are mostly dispersed randomly in the nanocomposite films.
1,308 citations
TL;DR: A variety of commercial or laboratory-engineered skin substitutes for wound healing are discussed, including electrospinning that allows the design and fabrication of biomimetic scaffolds that offer tremendous potential applications in wound healing of skin.
Abstract: One of the major applications of tissue-engineered skin substitutes for wound healing is to promote the healing of cutaneous wounds In this respect, many important clinical milestones have been reached in the past decades However, currently available skin substitutes for wound healing often suffer from a range of problems including wound contraction, scar formation, and poor integration with host tissue Engineering skin substitutes by tissue engineering approach has relied upon the creation of three-dimensional scaffolds as extracellular matrix (ECM) analog to guide cell adhesion, growth, and differentiation to form skin-functional and structural tissue The three-dimensional scaffolds can not only cover wound and give a physical barrier against external infection as wound dressing, but also can provide support both for dermal fibroblasts and the overlying keratinocytes for skin tissue engineering A successful tissue scaffold should exhibit appropriate physical and mechanical characteristics and provide an appropriate surface chemistry and nano and microstructures to facilitate cellular attachment, proliferation, and differentiation A variety of scaffolds have been fabricated based on materials ranging from naturally occurring ones to those manufactured synthetically This review discusses a variety of commercial or laboratory-engineered skin substitutes for wound healing Central to the discussion are the scaffolds/materials, fabrication techniques, and their characteristics associated with wound healing One specifically highlighted emerging fabrication technique is electrospinning that allows the design and fabrication of biomimetic scaffolds that offer tremendous potential applications in wound healing of skin
561 citations
TL;DR: This review summarizes recent progress in developments of the electrospun nanomaterials with applications in some predominant sensing approaches such as acoustic wave, resistive, photoelectric, optical, amperometric, and so on, illustrate with examples how they work, and discuss their intrinsic fundamentals and optimization designs.
547 citations
TL;DR: By constructing a novel Lyapunov-like matrix functional, the idea of delay fractioning is applied to deal with the addressed synchronization analysis problem and several delay-dependent sufficient conditions are obtained which ensure the asymptotic synchronization in the mean square sense for the discrete-time stochastic complex networks with time delays.
Abstract: In this paper, the problem of stochastic synchronization analysis is investigated for a new array of coupled discrete-time stochastic complex networks with randomly occurred nonlinearities (RONs) and time delays. The discrete-time complex networks under consideration are subject to: (1) stochastic nonlinearities that occur according to the Bernoulli distributed white noise sequences; (2) stochastic disturbances that enter the coupling term, the delayed coupling term as well as the overall network; and (3) time delays that include both the discrete and distributed ones. Note that the newly introduced RONs and the multiple stochastic disturbances can better reflect the dynamical behaviors of coupled complex networks whose information transmission process is affected by a noisy environment (e.g., Internet-based control systems). By constructing a novel Lyapunov-like matrix functional, the idea of delay fractioning is applied to deal with the addressed synchronization analysis problem. By employing a combination of the linear matrix inequality (LMI) techniques, the free-weighting matrix method and stochastic analysis theories, several delay-dependent sufficient conditions are obtained which ensure the asymptotic synchronization in the mean square sense for the discrete-time stochastic complex networks with time delays. The criteria derived are characterized in terms of LMIs whose solution can be solved by utilizing the standard numerical software. A simulation example is presented to show the effectiveness and applicability of the proposed results.
495 citations
TL;DR: Two kinds of robust distributed H"~-consensus filters are designed for the system with norm-bounded uncertainties and polytopic uncertainties, and two numerical simulation examples are used to demonstrate the effectiveness of the proposed distributed filters design scheme.
475 citations
TL;DR: The results indicate that a collagen-chitosan nanofiber matrix may be a better candidate for tissue engineering in biomedical applications such as scaffolds.
335 citations
TL;DR: Fully dense graphene nanosheet (GNS)/Al2O3 composites with homogeneously distributed GNSs of thicknesses ranging from 2.5 to 20 nm have been fabricated from ball milled expanded graphite and Al 2O3 by spark plasma sintering as mentioned in this paper.
326 citations
TL;DR: In this paper, a fractional variational iteration method with modified Riemann Liouville derivative is proposed to solve the fractional differential equations more efficiently, which avoids the term of fractional derivative and handles them as restricted variation.
325 citations
01 Jan 2010
TL;DR: In this article, the authors proposed three standard variational iteration algorithms for solving differential equations, integro-differential equations, fractional differential equations and differential-difference equations.
Abstract: This paper proposes three standard variational iteration algorithms for solving differential equations, integro-differential equations, fractional differential equations, fractal differential equations, differential-difference equations and fractional/fractal differential-difference equations. The physical interpretations of the fractional calculus and the fractal derivative are given and an application to discrete lattice equations is discussed. The paper then examines the acceleration of some iteration formulae with particular emphasis being placed on the exponential Pade approximant that is suggested for solitary solutions and the sinusoidal Pade approximant that is usually used for periodic and compacton solutions. The paper points out that there may not be any physical meaning to the exact solutions of many nonlinear equations and stresses the importance of searching for approximate solutions that satisfy both the equations and the appropriate initial/boundary conditions. The variational iteration method is particularly suitable for solving this kind of problems. Approximate initial/boundary conditions and point boundary initial/conditions are also discussed, with the variational iteration method being capable of recovering the correct initial/boundary conditions and finding the solutions simultaneously.
313 citations
TL;DR: The results suggest that as-prepared chitosan/silk fibroin (CS/SF) composite nanofibrous membranes could be a promising candidate for wound healing applications.
Abstract: Chitosan, a naturally occurring polysaccharide with abundant resources, has been extensively exploited for various biomedical applications, typically as wound dressings owing to its unique biocompatibility, good biodegradability and excellent antibacterial properties. In this work, composite nanofibrous membranes of chitosan (CS) and silk fibroin (SF) were successfully fabricated by electrospinning. The morphology of electrospun blend nanofibers was observed by scanning electron microscopy (SEM) and the fiber diameters decreased with the increasing percentage of chitosan. Further, the mechanical test illustrated that the addition of silk fibroin enhanced the mechanical properties of CS/SF nanofibers. The antibacterial activities against Escherichia coli (Gram negative) and Staphylococcus aureus (Gram positive) were evaluated by the turbidity measurement method; and results suggest that the antibacterial effect of composite nanofibers varied on the type of bacteria. Furthermore, the biocompatibility of murine fibroblast on as-prepared nanofibrous membranes was investigated by hematoxylin and eosin (H&E) staining and MTT assays in vitro, and the membranes were found to promote the cell attachment and proliferation. These results suggest that as-prepared chitosan/silk fibroin (CS/SF) composite nanofibrous membranes could be a promising candidate for wound healing applications.
285 citations
TL;DR: Fractional complex transform as mentioned in this paper was proposed to convert fractional differential equations into ordinary differential equations, so that all analytical methods devoted to advanced calculus can be easily applied to fractional calculus.
Abstract: Fractional complex transform is proposed to convert fractional differential equations into ordinary differential equations, so that all analytical methods devoted to advanced calculus can be easily applied to fractional calculus. Two examples are given.
TL;DR: The globally exponential stabilization problem is investigated for a general class of stochastic systems with both Markovian jumping parameters and mixed time-delays and it is shown that the desired state feedback controller can be characterized explicitly in terms of the solution to a set of LMIs.
Abstract: In this technical note, the globally exponential stabilization problem is investigated for a general class of stochastic systems with both Markovian jumping parameters and mixed time-delays. The mixed mode-dependent time-delays consist of both discrete and distributed delays. We aim to design a memoryless state feedback controller such that the closed-loop system is stochastically exponentially stable in the mean square sense. First, by introducing a new Lyapunov-Krasovskii functional that accounts for the mode-dependent mixed delays, stochastic analysis is conducted in order to derive a criterion for the exponential stabilizability problem. Then, a variation of such a criterion is developed to facilitate the controller design by using the linear matrix inequality (LMI) approach. Finally, it is shown that the desired state feedback controller can be characterized explicitly in terms of the solution to a set of LMIs. Numerical simulation is carried out to demonstrate the effectiveness of the proposed methods.
TL;DR: In this paper, a composite with core-shell structures consisting of polyaniline and carbon nanotubes was prepared via in situ polymerization of aniline monomers by using multi-walled carbon Nanotubes with minimized defects as templates.
TL;DR: The results indicate that this double-container drug delivery system is beneficial to reduce the burst release of the drug and the introduction of HNTs can significantly improve the tensile strength of the polymer nanofibrous mats.
Abstract: We report a novel electrospun composite nanofiber-based drug delivery system. In this study, halloysite nanotubes (HNTs) were first used to encapsulate a model drug, tetracycline hydrochloride. Then, the drug-loaded HNTs with an optimized encapsulation efficiency were mixed with poly(lactic-co-glycolic acid) (PLGA) polymer for subsequent electrospinning to form drug-loaded composite nanofibrous mats. The structure, morphology, and mechanical properties of the formed electrospun composite nanofibrous mats were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, and tensile testing. In vitro drug release behavior was examined using UV-vis spectroscopy. The biocompatibility of HNT-containing PLGA fibers was evaluated through cell culture and MTT assay. We show that the incorporation of HNTs within the nanofibrous mats does not significantly change the morphology of the mats. In addition, our results indicate that this double-container drug delivery system (both PLGA polymer and HNTs are drug carriers) is beneficial to reduce the burst release of the drug and the introduction of HNTs can significantly improve the tensile strength of the polymer nanofibrous mats. Given the proved biocompatibility of the HNT-containing PLGA nanofibers via MTT assay of cell viability and SEM observation of cell morphology, the drug loaded electrospun composite nanofibrous mats developed in this study may find various applications in tissue engineering and pharmaceutical sciences.
TL;DR: A thermal decomposition approach to the synthesis of water-soluble superparamagnetic manganese ferrite nanoparticles (NPs) for magnetic resonance (MR) imaging applications suggests that the developed MnFe(2)O(4) NPs can serve as a sensitive MR imaging contrast agent for liver imaging.
TL;DR: In this paper, an ultrathin multilayer (PVA/GO)n films were successfully fabricated by bottom-up layer-by-layer assembly of poly(vinyl alcohol) and exfoliated graphene oxide (GO) nanosheets.
Abstract: Despite great recent progress with graphene-based materials, the development of strong and cost-efficient multifunctional graphene-filled polymer composites has not yet to be achieved. A key challenge in the fabrication of nanoplatelet-filled polymer composites is the ability to realize the nanometer-level dispersion and the planar orientation of nanosheets in polymer matrices. In this report, ultrathin multilayer (PVA/GO)n films were successfully fabricated by bottom-up layer-by-layer (LBL) assembly of poly(vinyl alcohol) (PVA) and exfoliated graphene oxide (GO), in which exfoliated GO nanosheets were used as the building blocks. Typical tapping-mode atomic force microscope (AFM) and field emission scanning electron microscope (FESEM) images demonstrate an ordered arrangement of organic and inorganic layers. A significant enhancement of mechanical properties has been achieved, that is, a 98.7% improvement of elastic modulus (Er) and a 240.4% increase of hardness. This may be attributed to the well-define...
TL;DR: Combined flow cytometry, confocal microscopy, and magnetic resonance imaging studies show that the Mn3O4@SiO2(RBITC)–FA nanocomposites can specifically target cancer cells overexpressing FA receptors (FARs).
Abstract: Monodisperse silica-coated manganese oxide nanoparticles (NPs) with a diameter of ∼35 nm are synthesized and are aminated through silanization. The amine-functionalized core–shell NPs enable the covalent conjugation of a fluorescent dye, Rhodamine B isothiocyanate (RBITC), and folate (FA) onto their surface. The formed Mn3O4@SiO2(RBITC)–FA core–shell nanocomposites are water-dispersible, stable, and biocompatible when the Mn concentration is below 50 µg mL−1 as confirmed by a cytotoxicity assay. Relaxivity measurements show that the core–shell NPs have a T1 relaxivity (r1) of 0.50 mM−1 s−1 on the 0.5 T scanner and 0.47 mM−1 s−1 on the 3.0 T scanner, suggesting the possibility of using the particles as a T1 contrast agent. Combined flow cytometry, confocal microscopy, and magnetic resonance imaging studies show that the Mn3O4@SiO2(RBITC)–FA nanocomposites can specifically target cancer cells overexpressing FA receptors (FARs). Findings from this study suggest that the silica-coated Mn3O4 core–shell NPs could be used as a platform for bimodal imaging (both magnetic resonance and fluorescence) in various biological systems.
TL;DR: In this article, a Hamiltonian approach to nonlinear oscillators is suggested, where a conservative oscillator always admits a Hamiltonians invariant, H, which keeps unchanged during oscillation, and this property is used to obtain approximate frequency-amplitude relationship of a non-linear oscillator with acceptable accuracy.
14 Oct 2010
TL;DR: A novel protocol called LEACH-B (LEACH-Balanced) is presented, which has balanced the system energy consumption and has better performance of prolonging the network lifetime than LEACH protocol.
Abstract: Based on the analysis on the defect in LEACH including the fluctuation of the number of cluster heads and the ignorance of the node's residual energy, this paper presents a novel protocol called LEACH-B (LEACH-Balanced)At each round, after first selection of cluster head according to LEACH protocol, a second selection is introduced to modify the number of cluster head in consideration of node's residual energy As a result the number of cluster head is constant and near optimal per round The simulation by MATLAB shows that the improved protocol has balanced the system energy consumption and has better performance of prolonging the network lifetime than LEACH protocol
TL;DR: The results demonstrated that coaxial electrospun composite nanofibers had the characters of native extracellular matrix and may be used effectively as an alternative material for tissue engineering and functional biomaterials.
TL;DR: A novel humidity sensor was fabricated by electrospinning deposition of nanofibrous polyelectrolyte membranes as sensitive coatings on a quartz crystal microbalance (QCM) exhibiting high sensitivity and good linearity, and the resultant sensors exhibited a good reversible behavior and good long term stability.
Abstract: A novel humidity sensor was fabricated by electrospinning deposition of nanofibrous polyelectrolyte membranes as sensitive coatings on a quartz crystal microbalance (QCM). The results of sensing experiments indicated that the response of the sensors increased by more than two orders of magnitude with increasing relative humidity (RH) from 6 to 95% at room temperature, exhibiting high sensitivity, and that, in the range of 20-95% RH, the Log(Deltaf) showed good linearity. The sensitivity of fibrous composite polyacrylic acid (PAA)/poly(vinyl alcohol) (PVA) membranes was two times higher than that of the corresponding flat films at 95% RH. Compared with fibrous PAA/PVA membranes, the nanofibrous PAA membranes exhibited remarkably enhanced humidity sensitivity due to their high PAA content and large specific surface area caused by the formation of ultrathin nanowebs among electrospun fibers. Additionally, the resultant sensors exhibited a good reversible behavior and good long term stability.
TL;DR: The results demonstrate that emulsion electrospun fibers can successfully encapsulate proteins and release them in a sustained manner.
TL;DR: The present review is intended to direct the reader’s attention to the important subjects of synthetic and natural polymers with HA for bone tissue engineering.
Abstract: The fracture of bones and large bone defects owing to various traumas or natural ageing is a typical type of tissue malfunction. Surgical treatment frequently requires implantation of a temporary or permanent prosthesis, which is still a challenge for orthopaedic surgeons, especially in the case of large bone defects. Mimicking nanotopography of natural extracellular matrix (ECM) is advantageous for the successful regeneration of damaged tissues or organs. Electrospun nanofibre-based synthetic and natural polymer scaffolds are being explored as a scaffold similar to natural ECM for tissue engineering applications. Nanostructured materials are smaller in size falling, in the 1–100 nm range, and have specific properties and functions related to the size of the natural materials (e.g. hydroxyapatite (HA)). The development of nanofibres with nano-HA has enhanced the scope of fabricating scaffolds to mimic the architecture of natural bone tissue. Nanofibrous substrates supporting adhesion, proliferation, differentiation of cells and HA induce the cells to secrete ECM for mineralization to form bone in bone tissue engineering. Our laboratory (NUSNNI, NUS) has been fabricating a variety of synthetic and natural polymer-based nanofibrous substrates and synthesizing HA for blending and spraying on nanofibres for generating artificial ECM for bone tissue regeneration. The present review is intended to direct the reader’s attention to the important subjects of synthetic and natural polymers with HA for bone tissue engineering.
TL;DR: The chemical composition of organic matters (OMs) in domestic wastewater was determined in order to investigate types and origin of OMs, which will supply a more scientific basis for COD fractions of activated sludge models (ASMs) and wastewater treatment management.
TL;DR: This review reports some recent advances on the synthesis, self-assembly, and biofunctionalization of various dendrimer-based organic/inorganic hybrid nanoparticles for various biomedical applications, including but not limited to protein immobilization, gene delivery, and molecular diagnosis.
Abstract: This review reports some recent advances on the synthesis, self-assembly, and biofunctionalization of various dendrimer-based organic/inorganic hybrid nanoparticles (NPs) for various biomedical applications, including but not limited to protein immobilization, gene delivery, and molecular diagnosis. In particular, targeted molecular imaging of cancer using dendrimer-based organic/inorganic hybrid NPs will be introduced in detail.
TL;DR: In this paper, the ionic conductivity was found to be greatly dependent on the concentration of KOH and the interpenetrated polyvinylpyrrolidone in the PVA matrix.
TL;DR: The approach in this study has successfully demonstrated that these two techniques can be combined to produce double-layered tubular scaffolds containing both melt-spun macrofibers and electrospun submicron fibers.
TL;DR: The derived stability condition indicates that the smallest real part of eigenvalues of the Laplacian sub-matrix corresponding to the unpinned vertices can be used to measure the stabilizability of a digraph with a given pinned vertex set.
TL;DR: In this article, a formaldehyde sensor was fabricated by electrospinning deposition of nanofibrous polyethyleneimine (PEI)/poly(vinyl alcohol) (PVA) membranes as sensitive coatings on quartz crystal microbalance (QCM).
Abstract: A novel formaldehyde sensor was fabricated by electrospinning deposition of nanofibrous polyethyleneimine (PEI)/poly(vinyl alcohol) (PVA) membranes as sensitive coatings on quartz crystal microbalance (QCM). The morphology of the porous three-dimensional PEI/PVA membranes comprising fibers with diameter of 40 nm to 1.8 μm was controllable by tuning the compositions of polymers and solvents in PEI/PVA solutions. The resultant sensors showed a fast response to formaldehyde and a linear relationship upon increasing the formaldehyde concentrations due to the reversible interaction between formaldehyde molecules and amine groups of PEI. The sensor responses were reversible and reproducible towards formaldehyde in the concentration range of 10–255 ppm at room temperature. The sensitivity of fibrous membrane coated QCM sensors formed from the cosolvent of water and ethanol was three times higher than that of corresponded flat membrane coated QCM sensors when exposed to 255 ppm of formaldehyde. Relative humidity in testing chamber was proved to be the key parameter to affect the sensor sensitivity. Additionally, the fibrous PEI/PVA membrane coated QCM sensors exhibited a good selectivity to formaldehyde when tested with competing vapors.
TL;DR: A new robust H"~ filtering technique is developed for the addressed Ito-type discrete time-varying stochastic systems and relies on the forward solution to a set of recursive linear matrix inequalities and is therefore suitable for on-line computation.