Showing papers by "Xiamen University published in 2012"

Thermal conductivity of isotopically modified graphene

Abstract: Among other exotic properties graphene exhibits the highest thermal conductivity observed so far. This is true at least for graphene composed of only 12C atoms. However, it is now shown experimentally that regions of 13C atoms can substantially reduce the thermal conductivity. Aside from their fundamental importance, these results suggest that thermal conductivity can be tailored by varying the relative amounts of carbon isotopes used.

Light-Triggered Theranostics Based on Photosensitizer-Conjugated Carbon Dots for Simultaneous Enhanced-Fluorescence Imaging and Photodynamic Therapy

Abstract: National Key Basic Research Program (973 Project) [2010CB933901, 2011CB933100]; National Natural Scientific Fund [51102258, 20803040, 81028009, 31170961]; New Century Excellent Talent of Ministry of Education of China [NCET-08-0350]; Shanghai Science and Technology Fund [1052nm04100]; Ministry of Education

Molecular Communication and Networking: Opportunities and Challenges

Abstract: The ability of engineered biological nanomachines to communicate with biological systems at the molecular level is anticipated to enable future applications such as monitoring the condition of a human body, regenerating biological tissues and organs, and interfacing artificial devices with neural systems From the viewpoint of communication theory and engineering, molecular communication is proposed as a new paradigm for engineered biological nanomachines to communicate with the natural biological nanomachines which form a biological system Distinct from the current telecommunication paradigm, molecular communication uses molecules as the carriers of information; sender biological nanomachines encode information on molecules and release the molecules in the environment, the molecules then propagate in the environment to receiver biological nanomachines, and the receiver biological nanomachines biochemically react with the molecules to decode information Current molecular communication research is limited to small-scale networks of several biological nanomachines Key challenges to bridge the gap between current research and practical applications include developing robust and scalable techniques to create a functional network from a large number of biological nanomachines Developing networking mechanisms and communication protocols is anticipated to introduce new avenues into integrating engineered and natural biological nanomachines into a single networked system In this paper, we present the state-of-the-art in the area of molecular communication by discussing its architecture, features, applications, design, engineering, and physical modeling We then discuss challenges and opportunities in developing networking mechanisms and communication protocols to create a network from a large number of bio-nanomachines for future applications

High-Efficiency Photoelectrocatalytic Hydrogen Generation Enabled by Palladium Quantum Dots-Sensitized TiO2 Nanotube Arrays

Abstract: TiO(2) nanotube arrays (TNTAs) sensitized by palladium quantum dots (Pd QDs) exhibit highly efficient photoelectrocatalytic hydrogen generation. Vertically oriented TNTAs were prepared by a three-step electrochemical anodization. Subsequently, Pd QDs with uniform size and narrow size distribution were formed on TiO(2) nanotubes by a modified hydrothermal reaction (i.e., yielding nanocomposites of Pd QDs deposited on TNTAs, Pd@TNTAs). By exploiting Pd@TNTA nanocomposites as both photoanode and cathode, a substantially increased photon-to-current conversion efficiency of nearly 100% at λ = 330 nm and a greatly promoted photocatalytic hydrogen production rate of 592 μmol·h(-1)·cm(-2) under 320 mW·cm(-2) irradiation were achieved. The synergy between nanotubular structures of TiO(2) and uniformly dispersed Pd QDs on TiO(2) facilitated the charge transfer of photoinduced electrons from TiO(2) nanotubes to Pd QDs and the high activity of Pd QDs catalytic center, thereby leading to high-efficiency photoelectrocatalytic hydrogen generation.

Induction therapy with autologous mesenchymal stem cells in living-related kidney transplants: a randomized controlled trial.

Abstract: Key Science Research Project of Fujian Province, China [2009Y4001]; Key Laboratory of Fujian Province, China [2008J1006]

Transparent superhydrophobic/superhydrophilic TiO2-based coatings for self-cleaning and anti-fogging

Abstract: A stable titanate nanobelt (TNB) particle suspension was prepared by a hydrogen-bond-driven assembly of pre-hydrolysed fluoroalkylsilane (FAS) on its surface. A one-step electrophoretic deposition was applied to fabricate a transparent cross-aligned superhydrophobic TNB/FAS film on a conducting glass substrate. By controlling the deposition time, we have shown the transition between a “sticky” hydrophobic state (high contact angle with strong adhesion) and a “sliding” superhydrophobic state (high contact angle with weak adhesion). The optical transmittance can reach as high as 80% throughout most of the visible light region of the spectrum. These coatings have also displayed high chemical stability and self-cleaning ability. Upon heating the hydrophobic coatings at 500 °C, the TNB coating transforms into a porous TiO2(B) structure with superhydrophilic behavior and could be used for anti-fogging applications. With this TiO2-based system, we have demonstrated three different wetting states: superhydrophobicity with weak adhesion, high hydrophobicity with strong adhesion, and superhydrophilicity with immediate water spreading. Moreover, this work has also demonstrated superhydrophobic TNB/FAS films with high chemical stability and good self-cleaning performance and superhydrophilic pore-like TiO2(B) films with rapid water spreading and excellent anti-fogging ability.

High-Nuclearity 3d–4f Clusters as Enhanced Magnetic Coolers and Molecular Magnets

Abstract: Four 52-metal-ion 3d–4f cluster complexes featuring a common core of Ln42M10 (Ln = Gd3+, Dy3+; M = Co2+/3+, Ni2+) were obtained through self-assembly of the metal ions templated by mixed anions (ClO4– and CO32–). Magnetic studies revealed that the Gd42Co10 and Gd42Ni10 clusters exhibit the largest magnetocaloric effect (MCE) among any known 3d–4f complexes. Replacement of Gd3+ ions with anisotropic Dy3+ ions caused significant changes in the magnetic behavior of the clusters; both Dy42Co10 and Dy42Ni10 displayed slow relaxation of the magnetization.

Small Adsorbate-Assisted Shape Control of Pd and Pt Nanocrystals

Abstract: The shape control of noble metal nanocrystals is crucial to their optical properties and catalysis applications. In this Progress Report, the recent progress of shape-controlled synthesis of Pd and Pt nanostructures assisted by small adsorbates is summarized. The use of small strong adsorbates (e.g., I(-) , CO, amines) makes it possible to fabricate Pd and Pt nanostructures with not only well-defined surface structure but also morphologies that have not been achieved by other synthetic strategies. The roles of small adsorbates in shape control of Pd and Pt nanocrystals are discussed in the Report. Also presented in the Report are unique optical and catalytic properties of several Pd and Pt nanostructures (e.g., ultrathin Pd nanosheets, concave Pt octapod, concave Pd tetrahedra), as well as their bioapplications, to demonstrate the power of using small strong adsorbates in the shape control of Pt and Pd nanostructures.

Adaptive Hypergraph Learning and its Application in Image Classification

Abstract: Recent years have witnessed a surge of interest in graph-based transductive image classification. Existing simple graph-based transductive learning methods only model the pairwise relationship of images, however, and they are sensitive to the radius parameter used in similarity calculation. Hypergraph learning has been investigated to solve both difficulties. It models the high-order relationship of samples by using a hyperedge to link multiple samples. Nevertheless, the existing hypergraph learning methods face two problems, i.e., how to generate hyperedges and how to handle a large set of hyperedges. This paper proposes an adaptive hypergraph learning method for transductive image classification. In our method, we generate hyperedges by linking images and their nearest neighbors. By varying the size of the neighborhood, we are able to generate a set of hyperedges for each image and its visual neighbors. Our method simultaneously learns the labels of unlabeled images and the weights of hyperedges. In this way, we can automatically modulate the effects of different hyperedges. Thorough empirical studies show the effectiveness of our approach when compared with representative baselines.

Rectangular Bunched Rutile TiO2 Nanorod Arrays Grown on Carbon Fiber for Dye-Sensitized Solar Cells

Abstract: Because of their special application in photovoltaics, the growth of one-dimensional single-crystalline TiO(2) nanostructures on a flexible substrate is receiving intensive attention. Here we present a study of rectangular bunched TiO(2) nanorod (NR) arrays grown on carbon fibers (CFs) from titanium by a "dissolve and grow" method. After a corrosion process in a strong acid solution, every single nanorod is etched into a number of small nanowires. Tube-shaped dye-sensitized solar cells are fabricated by using etched TiO(2) NRs-coated CFs as the photoanode. An absolute energy conversion efficiency of 1.28% has been demonstrated under 100 mW cm(-2) AM 1.5 illumination. This work demonstrates an innovative method for growing bunched TiO(2) NRs on flexible substrates that can be applied in flexible devices for energy harvesting and storage.

Palladium nanocrystals enclosed by {100} and {111} facets in controlled proportions and their catalytic activities for formic acid oxidation

Abstract: This article reports a seed-mediated approach to polyhedral nanocrystals of Pd with controlled sizes, shapes, and different proportions of {100} to {111} facets on the surface. The success of this synthesis relies on the use of Pd nanocubes with different sizes as the seeds and the use of formaldehyde as a relatively mild reducing agent. By controlling the ratio of Pd precursor to the seed, we obtained uniform polyhedrons such as truncated cubes, cuboctahedrons, truncated octahedrons, and octahedrons in a purity approaching 100%. The sizes of these polyhedrons were determined by the edge length of the cubic seeds. Since these Pd polyhedrons were characterized by different proportions of {111} to {100} facets, they could serve as model catalysts to uncover the correlation between the surface structure and the catalytic performance for formic acid oxidation. Our measurements indicate that Pd nanocubes exhibited the highest maximum current density in the forward anodic scan, but the peak position was also located at a potential higher than those of the other polyhedrons. When both the current density and the operation potential are taken into consideration, Pd nanocubes with slight truncation at the corners become the best choice of catalyst for formic acid oxidation. Our study also revealed that the size of Pd polyhedrons had essentially no effect on the activity for formic acid oxidation.

Catalytic conversion of biomass-derived carbohydrates into fuels and chemicals via furanic aldehydes

Abstract: In recent years, substantial interest has been devoted to the conversion of biomass-derived carbohydrates into furanic aldehydes such as furfural, 5-hydroxymethylfurfural (HMF) and 5-halomethylfurfural, because these products are considered as important versatile intermediates that can be further transformed into a wide variety of high performance fuels and high value-added chemicals. However, low yields and high production costs that are due to the special chemical structures and properties of biomass-derived carbohydrates to a large extent have limited the practical production of furanic aldehydes. Recently, various catalytic conversion strategies have been developed to overcome these limitations. In this review, we systematically summarize and discuss catalytic conversion strategies from the perspective of catalysts and reaction solvents as well as formation mechanisms and influencing factors for the production of furanic aldehydes from biomass-derived carbohydrates. Meanwhile, we also outline the synthesis of furanic aldehyde-based fuels such as 2-methylfuran (MF), 2,5-dimethylfuran (DMF), 5-ethoxymethylfurfural (EMF) and alkanes and chemicals such as levulinic acid (LA), 2,5-diformylfuran (DFF) and 2,5-furandicarboxylic acid (FDCA). Moreover, some potential research orientations are proposed based on the major problems encountered in recent research.

GSK3-TIP60-ULK1 signaling pathway links growth factor deprivation to autophagy.

Abstract: 973 Program [2011CB910800]; National Natural Science Foundation of China [31130016, 30921005, 31000621]; Fundamental Research Funds for the Central Universities [2010121094]; Ministry of Education of China [B06016]

Rising CO2 and increased light exposure synergistically reduce marine primary productivity

Abstract: Carbon dioxide and light are two major prerequisites of photosynthesis. Rising CO2 levels in oceanic surface waters in combination with ample light supply are therefore often considered stimulatory to marine primary production(1-3). Here we show that the combination of an increase in both CO2 and light exposure negatively impacts photosynthesis and growth of marine primary producers. When exposed to CO2 concentrations projected for the end of this century(4), natural phytoplankton assemblages of the South China Sea responded with decreased primary production and increased light stress at light intensities representative of the upper surface layer. The phytoplankton community shifted away from diatoms, the dominant phytoplankton group during our field campaigns. To examine the underlying mechanisms of the observed responses, we grew diatoms at different CO2 concentrations and under varying levels (5-100%) of solar radiation experienced by the phytoplankton at different depths of the euphotic zone. Above 22-36% of incident surface irradiance, growth rates in the high-CO2-grown cells were inversely related to light levels and exhibited reduced thresholds at which light becomes inhibitory. Future shoaling of upper-mixed-layer depths will expose phytoplankton to increased mean light intensities(5). In combination with rising CO2 levels, this may cause a widespread decline in marine primary production and a community shift away from diatoms, the main algal group that supports higher trophic levels and carbon export in the ocean.

An Integrated Power Pack of Dye-Sensitized Solar Cell and Li Battery Based on Double-Sided TiO2 Nanotube Arrays

Abstract: We present a new approach to fabricate an integrated power pack by hybridizing energy harvest and storage processes. This power pack incorporates a series-wound dye-sensitized solar cell (DSSC) and a lithium ion battery (LIB) on the same Ti foil that has double-sided TiO(2) nanotube (NTs) arrays. The solar cell part is made of two different cosensitized tandem solar cells based on TiO(2) nanorod arrays (NRs) and NTs, respectively, which provide an open-circuit voltage of 3.39 V and a short-circuit current density of 1.01 mA/cm(2). The power pack can be charged to about 3 V in about 8 min, and the discharge capacity is about 38.89 μAh under the discharge density of 100 μA. The total energy conversion and storage efficiency for this system is 0.82%. Such an integrated power pack could serve as a power source for mobile electronics.

Proteolytic processing of Alzheimer’s β-amyloid precursor protein

Abstract: β-Amyloid precursor protein (APP) is a critical factor in the pathogenesis of Alzheimer's disease (AD). APP undergoes post-translational proteolysis/processing to generate the hydrophobic β-amyloid (Aβ) peptides. Deposition of Aβ in the brain, forming oligomeric Aβ and plaques, is identified as one of the key pathological hallmarks of AD. The processing of APP to generate Aβ is executed by β- and γ-secretase and is highly regulated. Aβ toxicity can lead to synaptic dysfunction, neuronal cell death, impaired learning/memory and abnormal behaviors in AD models in vitro and in vivo. Aside from Aβ, proteolytic cleavages of APP can also give rise to the APP intracellular domain, reportedly involved in multiple types of cellular events such as gene transcription and apoptotic cell death. In addition to amyloidogenic processing, APP can also be cleaved by α-secretase to form a soluble or secreted APP ectodomain (sAPP-α) that has been shown to be mostly neuro-protective. In this review, we describe the mechanisms involved in APP metabolism and the likely functions of its various proteolytic products to give a better understanding of the patho/physiological functions of APP.

Facile synthesis of manganese-oxide-containing mesoporous nitrogen-doped carbon for efficient oxygen reduction

Abstract: MOST of China [2011CB932403]; NSF of China [21131005, 20925103, 21021061, 21175042]; Fok Ying Tung Education Foundation [121011]; NSF of Fujian [2009J06005]; China Postdoctoral Science Foundation [20100480716]

Toward the Controlled Synthesis of Hexagonal Boron Nitride Films

Abstract: Atomically smooth hexagonal boron nitride (h-BN) layers have very useful properties and thus potential applications for protective coatings, deep ultraviolet (DUV) emitters, and as a dielectric for nanoelectronics devices. In this paper, we report on the growth of h-BN by a low-pressure chemical vapor deposition (LPCVD) process using diborane and ammonia as the gas precursors. The use of LPCVD allows synthesis of h-BN with a controlled number of layers defined by the growth conditions, temperature, time, and gas partial pressure. Furthermore, few-layer h-BN was also grown by a sequential growth method, and insights into the growth mechanism are described, thus forming the basis of future growth of h-BN by atomic layer epitaxy.

A Panel Data Approach for Program Evaluation — Measuring the Benefits of Political and Economic Integration of Hong Kong with Mainland China

Abstract: SUMMARY We propose a simple-to-implement panel data method to evaluate the impacts of social policy. The basic idea is to exploit the dependence among cross-sectional units to construct the counterfactuals. The cross-sectional correlations are attributed to the presence of some (unobserved) common factors. However, instead of trying to estimate the unobserved factors, we propose to use observed data. We use a panel of 24 countries to evaluate the impact of political and economic integration of Hong Kong with mainland China. We find that the political integration hardly had any impact on the growth of the Hong Kong economy. However, the economic integration has raised Hong Kong's annual real GDP by about 4%. Copyright © 2011 John Wiley & Sons, Ltd.

Numerical simulation of hot accretion flows ii nature, origin, and properties of outflows and their possible observational applications

Abstract: Hydrodynamical (HD) and magnetohydrodynamical (MHD) numerical simulations of hot accretion flows have indicated that the inflow accretion rate decreases inward. Two models have been proposed to explain this result. In the adiabatic inflow-outflow solution (ADIOS), this is because of the loss of gas in the outflow. In the alternative convection-dominated accretion flow model, it is thought that the flow is convectively unstable and gas is locked in convective eddies. We investigate the nature of the inward decrease of the accretion rate using HD and MHD simulations. We calculate various properties of the inflow and outflow such as temperature and rotational velocity. Systematic and significant differences are found. These results suggest that the inflow and outflow are not simply convective turbulence; instead, systematic inward and outward motion (i.e., real outflow) must exist. We have also analyzed the convective stability of MHD accretion flows and found that they are stable. These results favor the ADIOS scenario. We suggest that the mechanisms of producing outflow in HD and MHD flows are the buoyancy associated with the convection and the centrifugal force associated with the angular momentum transport mediated by the magnetic field, respectively. The latter is similar to the Blandford & Payne mechanism but no large-scale open magnetic field is required. We discuss some possible observational applications, including the Fermi bubble in the Galactic center and winds in active galactic nuclei and black hole X-ray binaries.

USP4 is regulated by AKT phosphorylation and directly deubiquitylates TGF-β type I receptor

Abstract: Ten Dijke and colleagues identify USP4 as a deubiquitylating enzyme (DUB) for the TGF-β receptor I in a screen for ubiquitin-specific proteases affecting TGF-β signalling. USP4, present in a complex with other DUBs, is regulated by AKT-mediated phosphorylation and is required for TGF-β-induced breast cancer cell migration and metastasis.

Selective Hydrogenation of α,β‐Unsaturated Aldehydes Catalyzed by Amine‐Capped Platinum‐Cobalt Nanocrystals

Abstract: 通讯作者地址: Zheng, NF (通讯作者),Xiamen Univ, Coll Chem & Chem Engn, State Key Lab Phys Chem Solid Surfaces, Xiamen 361005, Peoples R China 地址: 1. Xiamen Univ, Coll Chem & Chem Engn, State Key Lab Phys Chem Solid Surfaces, Xiamen 361005, Peoples R China 2. Xiamen Univ, Coll Chem & Chem Engn, Dept Chem, Xiamen 361005, Peoples R China 电子邮件地址: nfzheng@xmu.edu.cn; gfu@xmu.edu.cn

Decay of Dissipative Equations and Negative Sobolev Spaces

Abstract: We develop a general energy method for proving the optimal time decay rates of the solutions to the dissipative equations in the whole space. Our method is applied to classical examples such as the heat equation, the compressible Navier-Stokes equations and the Boltzmann equation. In particular, the optimal decay rates of the higher-order spatial derivatives of solutions are obtained. The negative Sobolev norms are shown to be preserved along time evolution and enhance the decay rates. We use a family of scaled energy estimates with minimum derivative counts and interpolations among them without linear decay analysis.

Quantitative analysis of the role played by poly(vinylpyrrolidone) in seed-mediated growth of Ag nanocrystals.

Abstract: This article presents a quantitative analysis of the role played by poly(vinylpyrrolidone) (PVP) in seed-mediated growth of Ag nanocrystals. Starting from Ag nanocubes encased by {100} facets as the seeds, the resultant nanocrystals could take different shapes depending on the concentration of PVP in the solution. If the concentration was above a critical value, the seeds simply grew into larger cubes still enclosed by {100} facets. When the concentration fell below a critical value, the seeds would evolve into cuboctahedrons enclosed by a mix of {100} and {111} facets and eventually octahedrons completely covered by {111} facets. We derived the coverage density of PVP on Ag(100) surface by combining the results from two measurements: (i) cubic seeds were followed to grow at a fixed initial concentration of PVP to find out when {111} facets started to appear on the surface, and (ii) cubic seeds were allowed to grow at reduced initial concentrations of PVP to see at which concentration {111} facets started...