Showing papers by "Nankai University published in 2007"
TL;DR: In this paper, simultaneous measurements of atmospheric organic and elemental carbon (OC and EC) were taken during winter and summer seasons at 2003 in 14 cities in China, and PM2.5 samples were analyzed for OC and EC by the Interagency Monitoring of Protected Visual Environments (IMPROVE) thermal/optical reflectance protocol.
Abstract: [1] Simultaneous measurements of atmospheric organic and elemental carbon (OC and EC) were taken during winter and summer seasons at 2003 in 14 cities in China. Daily PM2.5 samples were analyzed for OC and EC by the Interagency Monitoring of Protected Visual Environments (IMPROVE) thermal/optical reflectance protocol. Average PM2.5 OC concentrations in the 14 cities were 38.1 μg m−3 and 13.8 μg m−3 for winter and summer periods, and the corresponding EC were 9.9 μg m−3 and 3.6 μg m−3, respectively. OC and EC concentrations had summer minima and winter maxima in all the cities. Carbonaceous matter (CM), the sum of organic matter (OM = 1.6 × OC) and EC, contributed 44.2% to PM2.5 in winter and 38.8% in summer. OC was correlated with EC (R2: 0.56–0.99) in winter, but correlation coefficients were lower in summer (R2: 0.003–0.90). Using OC/EC enrichment factors, the primary OC, secondary OC and EC accounted for 47.5%, 31.7% and 20.8%, respectively, of total carbon in Chinese urban environments. More than two thirds of China's urban carbon is derived from directly emitted particles. Average OC/EC ratios ranged from 2.0 to 4.7 among 14 cities during winter and from 2.1 to 5.9 during summer. OC/EC ratios in this study were consistent with a possible cooling effect of carbonaceous aerosols over China.
992 citations
TL;DR: It is proposed that the strong adsorptive interaction between carbon nanotubes and nitroaromatics was due to the pi-pi electron-donor-acceptor (EDA) interaction between nitroroaromatic molecules (electron acceptors) and the highly polarizable graphene sheets (Electron donors) of carbon Nanotubes.
Abstract: Understanding adsorptive interactions between organic contaminants and carbon nanotubes is critical to both the environmental application of carbon nanotubes as special adsorbents and the assessment of the potential impact of carbon nanotubes on the fate and transport of organic contaminants in the environment. The adsorption of organic compounds with varied physical−chemical properties (hydrophobicity, polarity, electron polarizability, and size) to one single-walled carbon nanotube (SWNT) and two multiwalled carbon nanotubes (MWNTs) was evaluated. For a given carbon nanotube, the adsorption affinity correlated poorly with hydrophobicity but increased in the order of nonpolar aliphatic < nonpolar aromatics < nitroaromatics, and within the group of nitroaromatics, the adsorption affinity increased with the number of nitro-functional groups. We propose that the strong adsorptive interaction between carbon nanotubes and nitroaromatics was due to the π−π electron-donor–acceptor (EDA) interaction between nitr...
711 citations
TL;DR: In this article, the EMI shielding of the composite shows a reflection-dominant mechanism, while a shift from reflection to absorption was observed with increased SWCNT loading and frequency.
646 citations
08 May 2007
TL;DR: It is revealed that personalized search has significant improvement over common web search on some queries but it also has little effect on other queries, and even harms search accuracy under some situations.
Abstract: Although personalized search has been proposed for many years and many personalization strategies have been investigated, it is still unclear whether personalization is consistently effective on different queries for different users, and under different search contexts. In this paper, we study this problem and get some preliminary conclusions. We present a large-scale evaluation framework for personalized search based on query logs, and then evaluate five personalized search strategies (including two click-based and three profile-based ones) using 12-day MSN query logs. By analyzing the results, we reveal that personalized search has significant improvement over common web search on some queries but it also has little effect on other queries (e.g., queries with small click entropy). It even harms search accuracy under some situations. Furthermore, we show that straightforward click-based personalization strategies perform consistently and considerably well, while profile-based ones are unstable in our experiments. We also reveal that both long-term and short-term contexts are very important in improving search performance for profile-based personalized search strategies.
582 citations
TL;DR: The findings show that methanotrophy in the Bacteria is more taxonomically, ecologically and genetically diverse than previously thought, and that previous studies have failed to assess the full diversity of meethanotrophs in acidic environments.
Abstract: Bacteria that consume the greenhouse gas methane are potentially important players in the atmospheric budget, with the potential to sop up methane from the Earth's crust that would otherwise contribute to the atmospheric budget. Two new methane-utilizing bacteria have been isolated independently and both break new ground: unlike previous methanotrophic isolates, which are proteobacteria, they belong to the widely distributed Verrucomicrobia phylum. And both isolates display optimum growth and methane oxidation in remarkably acidic conditions, at pHs as low as 0.8 to 2.5. Acidimethylosilex fumarolicum SolV was isolated from a fuming vent on the Solfatara volcano near Naples, Italy, and Methylokorus infernorum from hot soil in the Hell's Gate (Tikitere) geothermal area of New Zealand. In spite of the fact that acidic environments support methane cycles, extreme acidophilic methanotrophs have so far resisted isolation. The isolation and initial genomic and physiological characterization of a bacterium belonging to the Verromicrobia displaying a growth and methane oxidation optimum of pH2—2.5 is described. Aerobic methanotrophic bacteria consume methane as it diffuses away from methanogenic zones of soil and sediment1. They act as a biofilter to reduce methane emissions to the atmosphere, and they are therefore targets in strategies to combat global climate change. No cultured methanotroph grows optimally below pH 5, but some environments with active methane cycles are very acidic2,3. Here we describe an extremely acidophilic methanotroph that grows optimally at pH 2.0–2.5. Unlike the known methanotrophs, it does not belong to the phylum Proteobacteria but rather to the Verrucomicrobia, a widespread and diverse bacterial phylum that primarily comprises uncultivated species with unknown genotypes. Analysis of its draft genome detected genes encoding particulate methane monooxygenase that were homologous to genes found in methanotrophic proteobacteria. However, known genetic modules for methanol and formaldehyde oxidation were incomplete or missing, suggesting that the bacterium uses some novel methylotrophic pathways. Phylogenetic analysis of its three pmoA genes (encoding a subunit of particulate methane monooxygenase) placed them into a distinct cluster from proteobacterial homologues. This indicates an ancient divergence of Verrucomicrobia and Proteobacteria methanotrophs rather than a recent horizontal gene transfer of methanotrophic ability. The findings show that methanotrophy in the Bacteria is more taxonomically, ecologically and genetically diverse than previously thought, and that previous studies have failed to assess the full diversity of methanotrophs in acidic environments.
527 citations
TL;DR: In this paper, three types of single-walled carbon nanotube (SWCNT) homogeneous epoxy composites with different SWCNT loadings (0.01-15%) were evaluated for electromagnetic interference (EMI) shielding effectiveness (SE) in the X-band range (8.2-12.4 GHz).
522 citations
463 citations
TL;DR: In this article, the synthesis and photophysical/electrochemical properties of a series of novel triphenylamine (TPA)-based organic dyes (TPAR1, TPAR2, TPARP4, and TPAR5) as well as their application in dye-sensitized nanocrystalline TiO2 solar cells were reported.
Abstract: We report here on the synthesis and photophysical/electrochemical properties of a series of novel triphenylamine (TPA)-based organic dyes (TPAR1, TPAR2, TPAR4, and TPAR5) as well as their application in dye-sensitized nanocrystalline TiO2 solar cells (DSCs). In the four designed dyes, the TPA group and the rhodanine-3-acetic acid take the role of the basic electron donor unit and the electron acceptor, respectively. It was found that introduction of a CH2CH− group into the TPA unit exhibited better photovoltaic performance due to the increase of the electron-density donor moiety and that introduction of a methine (−CHCH−) unit to the π bridge resulted in a red-shift and broadening of the absorption spectrum due to expansion of the π-conjugation system. Density functional theory (DFT) calculation indicated that the electron distribution moved from the donor unit to the electron acceptor under light irradiation, which means efficient intramolecular charge transfer. In particular, the DSCs based on TPAR4 sho...
377 citations
TL;DR: The genome reveals that NG80-2 is well equipped for adaptation into a wide variety of environmental niches, including oil reservoirs, by possessing genes for utilization of a broad range of energy sources, genes encoding various transporters for efficient nutrient uptake and detoxification, and genes for a flexible respiration system.
Abstract: The complete genome sequence of Geobacillus thermodenitrificans NG80-2, a thermophilic bacillus isolated from a deep oil reservoir in Northern China, consists of a 3,550,319-bp chromosome and a 57,693-bp plasmid. The genome reveals that NG80-2 is well equipped for adaptation into a wide variety of environmental niches, including oil reservoirs, by possessing genes for utilization of a broad range of energy sources, genes encoding various transporters for efficient nutrient uptake and detoxification, and genes for a flexible respiration system including an aerobic branch comprising five terminal oxidases and an anaerobic branch comprising a complete denitrification pathway for quick response to dissolved oxygen fluctuation. The identification of a nitrous oxide reductase gene has not been previously described in Gram-positive bacteria. The proteome further reveals the presence of a long-chain alkane degradation pathway; and the function of the key enzyme in the pathway, the long-chain alkane monooxygenase LadA, is confirmed by in vivo and in vitro experiments. The thermophilic soluble monomeric LadA is an ideal candidate for treatment of environmental oil pollutions and biosynthesis of complex molecules.
348 citations
TL;DR: Results show that TiO2 nanoparticles had a significantly stronger adsorption capacity for Cd than SP, which greatly enhanced the accumulation of Cd in carp after 25 d of exposure.
345 citations
TL;DR: The present results indicate that NH3BH3 along with Ni1-xPtx alloy hollow spheres may find some applications for small-scale on-board hydrogen storage and supply.
Abstract: In this paper, nest-like Ni1-xPtx (x = 0, 0.03, 0.06, 0.09, and 0.12) hollow spheres of submicrometer sizes have been prepared through a template-replacement route and investigated as catalysts for generating hydrogen from ammonia borane (NH3BH3). Experimental investigations have demonstrated that the obtained Ni1-xPtx alloy hollow spheres exhibit favorable catalytic activities for both the hydrolysis and the thermolysis of NH3BH3. It was found that, in the presence of the Ni0.88Pt0.12 catalyst, the hydrolysis of NH3BH3 causes a quick release of H2, while the thermal decomposition of NH3BH3 occurs at lowered temperatures with increased mass loss. The present results indicate that NH3BH3 along with Ni1-xPtx alloy hollow spheres may find some applications for small-scale on-board hydrogen storage and supply.
TL;DR: The present results clearly show that thinner Mg/MgH2 nanowires have a much lower desorption energy than that of thickernanowires or bulk Mg/(Mg/H2)H2, indicating that changes in kinetics and thermodynamics are expected if the diameters of the Nanowires are thinner than 30 nm.
Abstract: Mg nanowires with the diameters of 30−50 nm, 80−100 nm, and 150−170 nm, which were prepared via a vapor-transport method, exhibited enhanced kinetics for hydrogen absorption/desorption. The present results clearly show that thinner Mg/MgH2 nanowires have a much lower desorption energy than that of thicker nanowires or bulk Mg/MgH2, indicating that changes in kinetics and thermodynamics are expected if the diameters of the nanowires are thinner than 30 nm.
TL;DR: It is proved that 3,5-pyrazoledicarboxylic acid may be used as an effective bridging ligand to assemble lanthanide-based coordination polymers and the structure variation from the 3D porous framework to the 2D double-decker to the2D monolayer is attributed to the lanthanides contraction effect.
Abstract: 3,5-Pyrazoledicarboxylic acid (H3L) reacts with nitrate salts of lanthanide(III) (Ln = Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, and Er) under hydrothermal conditions to form a series of lanthanide polymers 1−9. These nine polymers have the same crystal system of monoclinic, but they exhibit three different kinds of metal−organic framework structures. The complexes {[Ln2(HL)3(H2O)4]·2H2O}n (Ln = Pr (1), Nd (2), and Sm (3)) were isostructural and exhibited porous 3D frameworks with a Cc space group. The complexes {[Ln2(HL)3(H2O)3]·3H2O}n (Ln = Eu (4), Gd (5), and Tb (6)) were isostructural and built 2D double-decker (2DD) frameworks with a P21/c space group. The complexes {[Ln(HL)(H2L)(H2O)2]}n ((Ln = Dy (7), Ho (8), and Er (9)) were also isostructural and formed 2D monolayer (2DM) frameworks with a P21/n space group. The structure variation from the 3D porous framework to the 2D double-decker to the 2D monolayer is attributed to the lanthanide contraction effect. Notably, six new coordination modes of 3,5-pyrazoled...
TL;DR: Specific network connectivity of these MOFs indicates that the metal centers represent the most significant and alterable factor in structural assembly, although they show reliable and similar geometries.
Abstract: To systematically explore the higher-dimensional network structures with mixed connectivity, a series of two-dimensional (2D) and three-dimensional (3D) metal-organic frameworks (MOFs) with unusual (3,6)-connected net topologies are presented. These crystalline materials include [{[Mn(btza)2(H2O)2].2 H2O}n] (1), [{[Zn(btza)2(H2O)2].2 H2O}n] (2), [{[Cu(btza)2].H2O}n] (3), and [{[Cd(btza)2].3 H2O}n] (4), which have been successfully assembled through a predesigned three-connected organic component bis(1,2,4-triazol-1-yl)acetate (btza) with a variety of octahedral metal cores based on the modular synthetic methodology. The topological paradigms shown in this work cover the 2D CdCl2, 3D (4(2).6)2(4(4).6(2).8(7).10(2)), and pyrite (pyr) types. That is, when properly treated with the familiar first-row divalent metal ions, btza may perfectly furnish the coordination spheres for effective connectivity to result in diverse (3,6)-connected nets. Beyond this, a detailed analysis of network topology for all known 3D (3,6)-connected frameworks in both inorganic and inorganic-organic hybrid materials is described. Specific network connectivity of these MOFs indicates that the metal centers represent the most significant and alterable factor in structural assembly, although they show reliable and similar geometries. In this context, the combination of the distinct d10 AgI ion with btza in different solvents affords two isomorphous MOFs [{[Ag(btza)].glycol}n] (5) and [{[Ag(btza)]CH3OH}n] (6) with a binodal 4-connected 3D SrAl2 (sra) topology. The network structures of MOFs 1-3 and 5 turn out to be more complicated and interesting if one considers the hydrogen bonding between the host coordination frameworks and the intercalated solvent molecules. Furthermore, the role of the included solvents in the generation and stabilization of MOFs 1-6 is also investigated.
TL;DR: It is proposed that the toxic critical value of soil Cd in inducing oxidative stress to wheat seedlings is between 3.3mgkg(-1) and 10mg kg(-1), which might be more sensitive or indicative than morphological observations in revealing the eco-toxicity of Cd.
TL;DR: The results indicate that the UV filters are not completely removed during WWRP treatment and may be carried over into the environment during the reuse applications.
TL;DR: In this paper, the as-prepared Co-B catalysts were in amorphous form with the composition of Co 2.3 B and had a good dispersion and coating condition, and the hydrogen generation measurement showed that the average hydrogen generation rate at 25 ∘ C was 1127.2 mL min - 1 g - 1 for unsupported Co−B catalyst, while it was 1268.1, 1482.1 and 2073.
TL;DR: This study suggests that SARS-CoV Mpro could serve as a new tag-cleavage endopeptidase for protein overproduction, and the WT SARS/WT Mpro is more appropriate for mechanistic characterization and inhibitor design.
TL;DR: Toxicity was mitigated by adding an antioxidant (glutathione), which suggests that a free radical—induced mechanism or another form of oxidative stress played a role in developmental toxicity.
Abstract: The present paper summarizes, to our knowledge, the first study regarding the developmental toxicity of stable buckminsterfullerene aggregates suspended in water (nC60) using zebrafish (Danio rerio) as a vertebrate model. Zebrafish embryo survival, hatching rate, heartbeat, and pericardial edema were noted and described within 96 h of exposure. Fullerol (a hydroxylated C60 derivative, C60(OH)16-18) at 50 mg/L did not exert toxicity to zebrafish embryos. In contrast, nC60 at 1.5 mg/L delayed zebrafish embryo and larval development, decreased survival and hatching rates, and caused pericardial edema. Toxicity was mitigated by adding an antioxidant (glutathione), which suggests that a free radical-induced mechanism or another form of oxidative stress played a role in developmental toxicity.
TL;DR: A highly efficient copper-catalyzed asymmetric insertion of α-diazoesters into N−H bonds has been realized by using chiral spiro bisoxazoline ligands, affording α-amino acid derivatives in high yields with excellent enantioselectivities.
Abstract: A highly efficient copper-catalyzed asymmetric insertion of α-diazoesters into N−H bonds has been realized by using chiral spiro bisoxazoline ligands, affording α-amino acid derivatives in high yields with excellent enantioselectivities.
TL;DR: The absorption and accumulation of Pb, Zn, Cu and Cd in some endurant weed plant species that survived in an old smeltery in Liaoning, China, were systematically investigated as discussed by the authors.
Abstract: The absorption and accumulation of Pb, Zn, Cu and Cd in some endurant weed plant species that survived in an old smeltery in Liaoning, China, were systematically investigated. Potential hyperaccumulative characteristics of these species were also discussed. The results showed that metal accumulation in plants differed with species, tissues and metals. Endurant weed plants growing in this contaminated site exhibited high metal adaptability. Both the metal exclusion and detoxification tolerance strategies were involved in the species studied. Seven species for Pb and four species for Cd were satisfied for the concentration time level standard for hyperaccumulator. Considering translocation factor (TF) values, one species for Pb, seven species for Zn, two species for Cu and five species for Cd possessed the characteristic of hyperaccumulator. Particularly, Abutilon theophrasti Medic, exhibited strong accumulative ability to four heavy metals. Although enrichment coefficients of all samples were lesser than 1 and the absolute concentrations didn't reach the standard, species mentioned above were primarily believed to be potential hyperaccumulators.
TL;DR: It was indicated that leaf SOD and POD activity of S. nigrum had a greater capacity than S. melongena to adapt to oxidative stress caused by Cd, and antioxidative defense in the Cd-hyperaccumulator might play an important role in Cd tolerance.
TL;DR: A novel amperometric glucose biosensor based on the nine layers of multilayer films composed of multi-wall carbon nanotubes, gold nanoparticles and glucose oxidase was developed and exhibited good reproducibility, long-term stability and the negligible interferences of ascorbic acid, uric acid and acetaminophen.
TL;DR: The results confirmed that the assembling process of multilayer films was simple to operate, the immobilized GOD displayed an excellent catalytic property to glucose, and GNp in the biosensing interface efficiently improved the electron transfer between analyte and electrode surface.
TL;DR: In this paper, the major source of PM10 in six northern China cities (Urumqi, Yinchuan, Taiyuan, Anyang, Tianjin and Jinan) was investigated.
TL;DR: A silica-supported ionic liquid proved to be an efficient heterogeneous catalyst for solventless synthesis of cyclic carbonates from epoxides and carbon dioxide under supercritical conditions, which requires no additional organic solvents either for the reaction or for the separation of product.
TL;DR: A novel nonlinear neural network (NN) predictive control strategy based on the new tent-map chaotic particle swarm optimization (TCPSO) is presented to enhance the convergence and accuracy of the TCPSO.
Abstract: In this letter, a novel nonlinear neural network (NN) predictive control strategy based on the new tent-map chaotic particle swarm optimization (TCPSO) is presented. The TCPSO incorporating tent-map chaos, which can avoid trapping to local minima and improve the searching performance of standard particle swarm optimization (PSO), is applied to perform the nonlinear optimization to enhance the convergence and accuracy. Numerical simulations of two benchmark functions are used to test the performance of TCPSO. Furthermore, simulation on a nonlinear plant is given to illustrate the effectiveness of the proposed control scheme
TL;DR: In this article, the pKa values of 16 1,3-dialkylimidazolium-type ionic liquid (IL) molecules were systematically measured by the overlapping indicator method at 25 °C in dimethyl sulfoxide (DMSO) solution.
Abstract: Equilibrium acidities of 16 1,3-dialkylimidazolium-type ionic liquid (IL) molecules (1−16) were systematically measured by the overlapping indicator method at 25 °C in dimethyl sulfoxide (DMSO) solution. The pKa values were observed to range from 23.4 for IL 12 to 19.7 for IL 6 (Tables 1 and 2), responding mainly to structural variations on the cation moiety. Excellent agreement between the spectrophotometrically determined pKa and that derived from NMR titration for 1,3,4,5-tetramethylimidazolium bis(trifluoromethanesulfonyl)imide (12) and the close match of the obtained pK values with the reported data in literature provide credence to the acidity measurements of the present work. The substituent effects at the imidazolium ring and the effects of counterions on the acidities of ionic liquids are discussed.
TL;DR: In this paper, a polyaniline (PAni)/SnO2 hybrid material was prepared by a hydrothermal method and characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM) and high-resolution transmission electron microscope (HRTEM).
Abstract: A polyaniline (PAni)/SnO2 hybrid material was prepared by a hydrothermal method and characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The XRD pattern suggested that PAni did not modify the crystal structure of SnO2, but SnO2 affected the crystallization of PAni to some extent. The gas sensitivity of the PAni/SnO2 hybrid was also studied to ethanol and acetone at operation temperatures of 30, 60 and 90 °C. It was found that the PAni/SnO2 hybrid material had gas sensitivity only when operated at 60 and 90 °C, and it showed a linear relationship between the responses and the concentrations of ethanol and acetone at 90 °C. The sensing mechanism was also discussed.