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ABSTRACT: Mechanical degradation of the electrode materials during electrochemical cycling remains a serious issue that critically limits the capacity retention and cyclability of rechargeable lithium-ion batteries. Here we report the highly reversible expansion and contraction of germanium nanoparticles under lithiation-delithiation cycling with in situ transmission electron microscopy (TEM). During multiple cycles to the full capacity, the GeNPs remained robust without any visible cracking despite ~250% volume changes, in contrast to the size dependent fracture of silicon nanoparticles upon the first lithiation. The comparative in situ TEM study of fragile silicon nanoparticles suggests that the high toughness of germanium nanoparticles can be attributed to the weak anisotropy of the lithiation strain at the reaction front. The tough germanium nanoparticles offer substantial potential for the development of durable, high-capacity and high-rate anodes for advanced lithium-ion batteries.
ACS Nano 03/2013; · 10.77 Impact Factor
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ABSTRACT: The rates of charging and discharging in lithium-ion batteries (LIBs) are critically controlled by the kinetics of Li insertion and extraction in solid-state electrodes. Silicon is being intensively studied as a high-capacity anode material for LIBs. However, the kinetics of Li reaction and diffusion in Si remain unclear. Here we report a combined experimental and theoretical study of the lithiation kinetics in individual Si nanowires. By using in situ transmission electron microscopy, we measure the rate of growth of a surface layer of amorphous LixSi in crystalline Si nanowires during the first lithiation. The results show the self-limiting lithiation, which is attributed to the retardation effect of the lithiation-induced stress. Our work provides a direct measurement of the nanoscale growth kinetics in lithiated Si, and has implications on nanostructures for achieving the high capacity and high rate in the development of high performance LIBs.
ACS Nano 12/2012; · 10.77 Impact Factor
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LiFei Wei, Hui Yang,
ZhaoHong Xie,
ShaoNan Yang,
HongNa Yang,
CuiPing Zhao,
Ping Wang,
ShunLiang Xu,
JunYing Miao,
BaoXiang Zhao,
JianZhong Bi
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ABSTRACT: Excessive extracellular deposition of amyloid- peptide (Aβ) in the brain is the pathological hallmark of Alzheimer's disease (AD). Cumulative evidence indicates that autophagy is involved in the metabolism of Aβ and pathogenesis of AD. However, the molecular mechanism underlying the pathogenesis of AD is not yet well defined, and there has been no effective treatment for AD. We recently found that long-term treatment with a butyrolactone derivative 3-benzyl-5-((2-nitrophenoxy) methyl)-dihydrofuran- 2(3 H)-one (3BDO) increased levels of insulin-degrading enzyme and neprilysin, suppressed autophagy via an mTOR pathway, lowered levels of Aβ, and prevented AD-like cognitive deficits in the AβPP/PS1 double transgenic mouse model. Therefore, our findings suggest that 3BDO may be beneficial in the prevention and treatment of AD.
Journal of Alzheimer's disease: JAD 03/2012; 30(3):531-43. · 3.74 Impact Factor
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Hui Yang,
Shan Huang,
Xu Huang,
Feifei Fan,
Wentao Liang,
Xiao Hua Liu,
Long-Qing Chen,
Jian Yu Huang,
Ju Li,
Ting Zhu,
Sulin Zhang
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ABSTRACT: Recent independent experiments demonstrated that the lithiation-induced volume expansion in silicon nanowires, nanopillars, and microslabs is highly anisotropic, with predominant expansion along the <110> direction but negligibly small expansion along the <111> direction. The origin of such anisotropic behavior remains elusive. Here, we develop a chemomechanical model to study the phase evolution and morphological changes in lithiated silicon nanowires. The model couples the diffusive reaction of lithium with the lithiation-induced elasto-plastic deformation. We show that the apparent anisotropic swelling is critically controlled by the orientation-dependent mobility of the core-shell interface, i.e., the lithiation reaction rate at the atomically sharp phase boundary between the crystalline core and the amorphous shell. Our results also underscore the importance of structural relaxation by plastic flow behind the moving phase boundary, which is essential to quantitative prediction of the experimentally observed morphologies of lithiated silicon nanowires. The study sheds light on the lithiation-mediated failure in nanowire-based electrodes, and the modeling framework provides a basis for simulating the morphological evolution, stress generation, and fracture in high-capacity electrodes for the next-generation lithium-ion batteries.
Nano Letters 03/2012; 12(4):1953-8. · 13.20 Impact Factor
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Chun-Yu Deng,
Su-Juan Kuang,
Fang Rao, Hui Yang,
Xian-Hong Fang,
Zhi-Xin Shan,
Xiao-Hong Li,
Zhi-Ling Zhou,
Qiu-Xiong Lin,
Min Yang,
Shu-Lin Wu,
Xi-Yong Yu,
Shu-Guang Lin
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ABSTRACT: Ranolazine is mainly used to treat patients with chronic stable angina in clinical practice. However, ranolazine does not lower significantly systemic blood pressure. The direct effect of ranolazine on vascular tone remains unknown. In the present study, we investigated the vascular effects and mechanisms of action of ranolazine in isolated rat intrarenal arteries. Rings of intrarenal arteries were mounted in a small vessel myography using two stainless steel wires for the measurement of isometric tension. L-type Ca²⁺ currents were recorded in isolated single renal arterial smooth muscle cells using patch clamp techniques in whole-cell mode. Ranolazine induced concentration-dependent relaxations in rings contracted with phenylephrine, but ranolazine failed to cause any relaxation in rings pre-contracted by U46619, 5-HT or endothelin-1. Ranolazine also induced relaxations in norepinephrine pre-contracted rings. Yohimbine failed to induce relaxation in rings pre-contracted by norepinephrine. Propranolol did not affect ranolazine-induced relaxation but the relaxant effect of ranolazine was much less than that of prazosin. Ranolazine-induced relaxations were slight but significantly attenuated by endothelial denudation. Partial inhibition was observed in endothelium-intact arteries exposed to a combination of iberiotoxin and apamin. Ranolazine at higher concentration (>30 μM) inhibited Ca²⁺-induced contraction in a noncompetitive manner. Ranolazine reduced L-type Ca²⁺ currents at potentials between -30 and 50 mV in isolated renal artery myocytes. Therefore it can be said that ranolazine has significant α₁-adrenergic receptor and weak calcium channel antagonistic effects in rat intrarenal arteries.
European journal of pharmacology 03/2012; 683(1-3):211-6. · 2.59 Impact Factor
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ABSTRACT: To construct a lentiviral vector of miR-335 gene and verify the target gene of miR-335.
The precursor sequence of miR-335 gene was amplified from the genomic DNA by PCR and cloned into the lentiviral vector PLVTHM labeled with GFP. Real-time quantitative RT-PCR was used to detect miR-335 and RASA1 expression in different colorectal cancer cell lines. A recombinant vector psiCHECK-2-RASA1 containing RASA1 3'UTR was constructed followed by site-directed mutagenesis of RASA1 3'UTR to establish the vector psiCHECK-2-RASA1-Mut. Co-transfection of hsa-mir-335 or a NC with these recombined vectors in HEK293A and SW480 cells was performed, and dual-luciferase reporter assay was utilized to examine the changes in luciferase activities. The recombinant PLVTHM-miR335 plasmid was packaged into mature lentivirus by 293FT cells and used to infect SW620 cells. Flow cytometry was employed for sorting the GFP+ cells. The expression of miR-335 and RASA1 were determined by qRT-PCR, and Western blotting was used to detect the expression of RASA1 protein in SW620 cell lines.
The recombinant lentiviral vector PLVTHM-miR335, psiCHECK-2-RASA1 and the mutation expression vector psiCHECK-2-RASA1-Mut were successfully constructed. Dual-luciferase reporter assay showed that miR-335 decreased luciferase activity in cells co-transfected with psiCHECK-2-RASA1. The expression of miR-335 in SW620 cells infected with the lentivirus PLVTHM-miR335 was significantly increased, but the expression of RASA1 showed only slight changes. Overexpression of miR-335 suppressed the expression of RASA1 protein in SW620 cells.
We have successfully constructed the lentiviral vector containing mir-335 gene and a SW620 cell line with miR-335 overexpression. MiR-335 can suppress RASA1 gene expression by targeting the specific sequence of RASA1 3'UTR.
Nan fang yi ke da xue xue bao = Journal of Southern Medical University 03/2012; 32(3):306-11.
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ABSTRACT: To isolate CD133(+) hematopoietic progenitor cells from human umbilical cord blood and optimize the culture condition for maintaining their stem cell characteristics.
CD133(+) hematopoietic progenitor cells were isolated from human umbilical cord blood using magnetic cell sorting system, and the cells were detected by flow cytometry. Four methods were used for culturing cells. After 8 weeks' culture, cytomorphology, flow cytometry, immunocytochemistry and immunofluorescence assay were used to identify the characteristics of the stem cells.
Over 80% of CD133(+) hematopoietic progenitor cells were isolated from human umbilical cord blood using magnetic cell sorting system. The cells were effectively expanded using optimized serum-free medium after 8 weeks of cell culture, whereas the cells in other media differentiated into adherent cells in a poor state.
The optimized serum-free medium allows effective expansion of CD133(+) hematopoietic progenitor cells that maintain stem cell characteristics after a long-term culture.
Nan fang yi ke da xue xue bao = Journal of Southern Medical University 03/2012; 32(3):349-53.
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ABSTRACT: In this paper the feasibility of enhanced electricity generation of microbial fuel cell fed surplus sludge by additional enzymes (neutral protease and alpha-amylase) was discussed. The effect of dosage of additional enzyme on characteristics of electricity generation of the surplus sludge microbial fuel cell (SSMFC) and the reduction of surplus sludge were investigated. The results indicated that the maximum output power destiny of the group of experiment was higher than that of control under the same condition. Moreover, the maximum output power density, coulomb efficiency, efficiency of reducing TCOD, efficiency of reducing TSS and efficiency of reducing VSS reached up to 507 W x m(-2) (700 mW x m(-2)), 3.98% (5.11%), 88.31% (94.09%), 83.18% (98.02%) and 89.03% (98.80%) respectively for protease (alpha-amylase) at the dosage of 10 mg x g(-1). This study demonstrated that additional enzyme greatly enhanced the electricity generation of MFC with simultaneous accomplishments of sludge treatment, providing a novel approach for the practical application of microbial fuel cell.
Huan jing ke xue= Huanjing kexue / [bian ji, Zhongguo ke xue yuan huan jing ke xue wei yuan hui "Huan jing ke xue" bian ji wei yuan hui.] 01/2012; 33(1):216-21.
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ABSTRACT: The preparation of carbon-supported Pt–Ni alloy catalysts at a 40 wt% total metal loading and with high Ni content within the alloys and their electrocatalysis for the oxygen reduction reaction has been studied. Emphasis is placed on the methanol-tolerant oxygen reduction on as-prepared alloy catalysts and their application in direct methanol fuel cells. It was found that as-prepared alloy catalysts have single-phase disordered structures and small particle sizes with a relatively narrow size distribution even at 40 wt% loading. As compared to pure Pt/C catalyst for oxygen reduction, such alloy catalysts exhibited enhanced electrocatalytic activities in pure acidic electrolyte and significantly enhanced electrocatalytic activities in methanol-containing electrolyte. The high methanol tolerance of Pt–Ni alloy catalysts during oxygen reduction could be ascribed to a lowered activity of methanol oxidation, which may originate from the composition effect and the disordered structure of the alloy catalysts. Fuel cell tests confirmed that as-prepared Pt–Ni alloy catalysts for oxygen reduction are more active than a commercial Pt/C catalyst with the same metal loading and that the maximum activity was found with a Pt/Ni atomic ratio of 2:1, which is similar to results in half-cell tests.
Journal of Electroanalytical Chemistry 04/2005; 576(2):305-313. · 2.58 Impact Factor
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ABSTRACT: The oxygen-reduction kinetics on Vulcan XC-72 carbon-supported nanosized Pt−Cr alloy catalysts were studied using the porous rotating disk electrode technique in pure and methanol-containing electrolytes. The Vulcan XC-72 carbon-supported Pt−Cr alloy catalysts with different Pt/Cr atomic ratios were prepared via a Pt−carbonyl route. X-ray diffraction data showed that the as-prepared nanosized Pt−Cr alloy catalysts mainly have the disordered structures (solid solution) and that the lattice parameter decreases with the increase in Cr content. Energy-dispersive X-ray analysis indicated that the catalyst compositions are nearly the same as the nominal ones. The obtained Pt−Cr alloy nanoparticles are well dispersed on the surface of carbon with a relatively narrow size distribution. For example, the mean particle size of the as-prepared Pt−Cr (1:1)/C catalyst with 20 wt % metal loading is about 3.1 nm in diameter with a standard deviation of 1.3 nm, and the particle size distribution is relatively narrow. As compared to the Pt/C catalyst, the bimetallic alloy catalysts with the different Pt/Cr atomic ratios showed slightly enhanced mass activity (MA) for the oxygen reduction reaction (ORR); however, the significant enhancement in the specific activity (SA) by a factor of about 1.5−3 for the ORR was found on the Pt−Cr alloy catalysts in pure HClO4 solution. This enhancement in SA of the Pt-based catalysts was correlated to the changes in the lattice parameter and Pt/Cr surface composition. Moreover, the bimetallic Pt−Cr alloy catalysts with the different Pt/Cr atomic ratios exhibited much higher methanol tolerance during the ORR than the Pt/C catalyst. Furthermore, the catalytic activity for methanol oxidation on the Pt−Cr alloy catalysts was much lower than that on the Pt/C catalyst. Thus, the high methanol tolerance of the carbon-supported Pt−Cr alloy catalysts for the ORR can be ascribed to the weak adsorption of methanol induced by the presence of Cr atoms in the alloys.
The Journal of Physical Chemistry B 01/2004; 108(6):1938–1947. · 3.70 Impact Factor
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Zhao-Yin Fang, Hui Yang,
Jin Qi,
Jing Zhang,
Li-Wei Sun,
Jing-Yu Tang,
Li Ma,
Zeng-Qing Du,
Ai-Hua He,
Jian-Ping Xie,
Yi-Yu Lu,
Zhen-Zhou Ji,
Bao-Quan Zhu,
Hai-Yan Wu,
Si-En Lin,
Hua-Ping Xie,
Dixie D Griffin,
Bernard Ivanoff,
Roger I Glass,
Jon R Gentsch
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ABSTRACT: As part of a national rotavirus surveillance activity, we collected fecal specimens from 3,177 children with acute diarrhea in 10 regions of China between April 1998 and April 2000 and screened them for rotavirus. Rotavirus was detected in 41% (n = 1,305) of specimens, and in these, G1 was the predominant serotype (72.6%), followed by G3 (14.2%), G2 (12.1%), G4 (2.5%), G9 (0.9%), and G untypeable (0.7%). Among 327 G-typed strains tested for P genotype, 14 different P-G combinations were identified, with the globally common strains P[8]G1, P[4]G2, P[8]G3, and P[8]G4 representing 75.6% of all typed rotavirus strains. Among the uncommon strains, 11 were P[6]G9, and others included P[6]G1, P[6]G3, and five novel P-G combinations (P[9]G1, P[4]G1, P[4]G3, P[4]G4, and P[8]G2). Our results indicate that while the common rotavirus strains remain predominant, the diversity of strains is much greater than was previously recognized.
Journal of Clinical Microbiology 06/2002; 40(5):1875-8. · 4.15 Impact Factor
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ABSTRACT: The nanosized Ag/Cu/HA powder is thermodynamically unstable and easily congregates during storing, which may make it lose the nanomaterial's properties. In this work, the performances of Ag/Cu/HA during storing were studied. The Ag/Cu/HA powders were prepared using a one-step co-precipitation method. The effects of storing on powder microstructures were investigated. The microstructures of Ag/Cu/HA powders were characterized by X-ray diffraction and scanning electron microscopy. The results show that the diffraction intensities and the sizes of the calcined Ag/Cu/HA powders are reduced during storing. Storing makes the diffraction angles of 0 0 2 and 3 0 0 peaks decreased and makes that of 2 1 1 peak increased. In addition, storing increases the crystal growth along the c-axis without the effect on the crystal morphology of powders. The stored Ag/Cu/HA powders can induce the formation of new HA crystal the same as the stored Ag/Cu/HA powders with platelet morphology and low intensity and crystallinity similar to nature bone.
Ceramics International.
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ABSTRACT: This paper proposes an adaptive video smoothing and rebuffering algorithm for video transmission in best-effort, low-bandwidth networks. Our algorithm, which is derived from a “dynamic” extension of the network calculus, (1) detects whether playback disruptions are inevitable and, if so, schedules a rebuffering action with minimal rebuffering delay and (2) computes a conservative transmission schedule that ensures continuous playback while minimizing consumption of network available bandwidth. NS-2 simulation results show that, compared to an aggressive transmission strategy, our method can greatly reduce bandwidth consumption and, compared to a simple rebuffering strategy with the same bandwidth consumption, our method can effectively reduce total playback delay while also reducing the number of rebuffering events.
Computer Networks.
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ABSTRACT: The ternary Sm(III) complex with the salicylic acid (HSal) and o-phenanthroline (Phen) has been prepared. The photoluminescence intensity of the complex Sm(Sal)3(Phen) is enhanced by more than two hundred times with respect to that of the binary complex Sm(Sal)3(H2O)2. It is confirmed by Sm(III) content titration and the spectra of IR, UV–vis and fluorescence that the second ligand, Phen, also coordinates with the Sm3+ ion. The second ligand Phen shows enhancement effect on the fluorescence of the complex. These observations are discussed in detail and the results are rationalized.
Journal of Alloys and Compounds.
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ABSTRACT: To meet the demands for high power micro-electronic devices, two silicon-based micro-direct methanol fuel cell (μDMFC) stacks consisting of six individual cells with two different anode flow fields were designed, fabricated and evaluated. Micro-electronic–mechanical-system (MEMS) technology was used to fabricate both flow field plate and fuel distribution plate on the silicon wafer. Experimental results show that either an individual cell or a stack with double serpentine-type flow fields presents better cell performance than those with pin-type flow fields. A μDMFC stack with double serpentine-type flow fields generates a peak output power of ca. 151 mW at a working voltage of 1.5 V, corresponding to an average power density of ca. 17.5 mW cm−2, which is ca. 20.7% higher than that with pin-type flow fields. The volume and weight of the stacks are only 5.3 cm3 and 10.7 g, respectively. Such small stacks could be used as power sources for micro-electronic devices.
Journal of Power Sources.
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ABSTRACT: Owing to its molecular membrane structure, tearing is the predominant fracture mode for a monolayer graphene. Yet, the tearing mechanics of monolayer graphene as a two-dimensional (2D) crystal remains poorly understood. Here, we performed molecular dynamics simulations with reactive force field to determine the fracture path of monolayer graphene under tearing. Our simulations revealed that the chemomechanical tearing conditions play a regulatory role on the edge structures of graphene nanoribbons (GNRs) produced by tearing. In vacuum, the resulting GNR features the armchair edge, whereas in the presence of chemical additives (such as oxygens) to the fracture surface, the resulting GNR edge changes from armchair to zigzag. In addition, due to the large in-plane stretching to out-of-plane bending stiffness ratio of monolayer graphene, tearing causes local bending at the crack tip, giving rise to a fracture mode mixity that also modulates the fracture path. In addition to provide an atomistic understanding of tearing mechanics of 2D crystal membranes, our findings shed light on chemomechanical engineering of GNRs with controlled edge structures.
Phys. Rev. B. 85(19).
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ABSTRACT: Hydroxyapatite doped with lanthanum (La/HAP) was prepared using co-precipitation method in this study. The effects of the concentration of La3+, stirring, aging time, hydrothermal treatment and calcination temperature on orient growth of the La/HAP were investigated. The phase composition of the La/HAP was analyzed by means of X-ray diffraction (XRD). The parameter (c/a) values of the orient growth of the La/HAP were calculated based on XRD data. The results show that the orient growth of La/HAP crystal is slightly affected by the concentration of La3+ in reaction solution whereas the growth of the crystal is closely related to the aging time and the calcination temperature. As the calcination temperature changes from 100 °C to 750 °C, the La/HAP crystal tends to grow along a-axis. The tendency of the crystal growth in the direction of c-axis becomes obvious at 70 °C as aging time extends. However, stirring appears to restrain the growth of crystal in c-axis. The hydrothermal treatment at 125 °C seems helpful for getting a low c/a value crystal and changes the La/HAP from needle shape to rod one. The direction of the c-axis of the La/HAP lattice seems to be the same as that of the long-axis of the La/HAP nanoparticles. The as-synthesized La/HAP powder mainly consists of HAP phase with slight La2O3 phase and has good thermostability.
Journal of Materials Processing Technology 207:276-282. · 1.78 Impact Factor
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ABSTRACT: La/HAP composite powder, a novel bioactive material, was prepared using co-precipitation method. The La/HAP coating was obtained for the first time through the dip-coating method, starting from the sols of La/HAP and TiO2 particles. The compositions and coating of as-produced La/HAP composite powder sintered at temperatures from 300 to 750 °C were analyzed by means of X-ray diffraction (XRD). The changes of the ion groups in as-prepared La/HAP composite powder were characterized by using Fourier transform infrared (FTIR) spectroscopy. Their surface morphologies were observed by means of scanning electron microscope (SEM). The results show that the La/HAP composite powder has higher thermostability than pure HAP powder and La can refine HAP particle and restrain the decomposition of HAP. Consequently, in coating process the heat-treatment temperature is lower (750 °C) using the synthesized La/HAP powder than that using pure HAP (900 °C). The La/HAP coating mainly contains HAP, TiP or Ti3P5 and TiO2 phases as well as a little CaTiO3 crystal, a very ideal composition to enhance bioactivity of biomaterials. These unique properties of the La/HAP composite powder are beneficial to enhance the strength and bioactivity of coating when it is used as a starting material in coating process.
Applied Surface Science 254(2):425-430. · 2.10 Impact Factor
