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Horizontal drilling and hydraulic fracturing have been proven to significantly increase production from tight oil formations, however, one of the characteristics of these reservoirs is high production declining rate. In the long term, it is necessary to increase the development efficiency of block matrix, many studies have shown that spontaneous imbibition is a potential way. In addition, precisely predicting the behavior of the imbibition recovery under different viscosity ratios is thus critically important. The goals of this paper include theoretically and experimentally investigating the effect of the viscosity on the imbibition recovery. In this paper a novel pore-scale spontaneous imbibition model is established by two steps. At first, the spontaneous imbibition equation in a single capillary tube considering that immobile oil is established based on Hagen Poiseuille formula. Then, pore-scale spontaneous imbibition model based on fractal theory has been derived. In addition, the corresponding spontaneous imbibition tests have been conducted on sandstone natural cores collected from Xinjiang oilfield. The predictions of the imbibition recovery by the proposed model have been validated by comparing them with the experiments conducted. Data of cores H-56 and H-39 are used to comparing the calculated imbibition recovery with the measured imbibition recovery. Under four different oil/water viscosity ratio, 0.5, 1, 5 and 10, the relative errors between calculated data and measured data are less than 7%. And both the theoretical and experimental results show that the viscosity ratio of the mixed oil and brine has a significant effect on the spontaneous imbibition recovery. The predicted and experimental results demonstrate that a higher imbibition recovery corresponds to a lower oil/brine viscosity ratio. In addition, rate of spontaneous imbibition has a significant decline which is the same as the result of the calculation. In general, since the established model has a high precision, it can be used to analyze the effects of different parameters like the contact angle, the interfacial tension and other structural parameters and the results can be useful for understanding the spontaneous imbibition law. What's more, the conclusion can guide the surfactant screening in surfactant-aided imbibition schemes.

A dinuclear copper(II) complex (1) of a Schiff-base ligand L [2-((Z)-(3-((3-((Z)-2-hydroxybenzylideneamino)propyl)(pyridin-4-yl)amino)propylimino)methyl)phenol] was synthesized and characterized. Complex 1 has a [2+2] ring structure formed by two ligands and two central atoms, and each central metal atom lies in a distorted tetrahedral environment. The in vitro DNA binding studies of 1 with calf thymus-DNA were carried out by UV/Vis, fluorescence and circular dichroism spectroscopic methods, competitive groove-binding test, and molecular docking. Complex 1 efficiently cleaved supercoiled pUC19 DNA. As evidenced by the consistent experimental and theoretical outcomes, the copper(II) complex interacted with DNA by both partial intercalation and minor-groove binding.

Dimercaptopropanesulfonic acid (DMPS) has been approved for the treatment of arsenic poisoning through promoting arsenic excretion and modulating arsenic species. To clarify how DMPS regulates the excretion of arsenic species, we investigated the effects of DMPS on the biomethylation of arsenite (As(3+)) in HepG2 cells. In the experiments, we found that DMPS at low concentrations dramatically decreased the content of arsenic in HepG2 cells and inhibited the cellular methylation of As(3+). Three aspects, the expression of human arsenic (III) methyltransferase (hAS3MT), the accumulation of cellular reactive oxygen species (ROS) and the in vitro enzymatic methylation of arsenic, were considered to explain the reasons for the inhibition of DMPS in arsenic metabolism. The results suggested that DMPS competitively coordinated with As(3+) and monomethylarsonous acid (MMA(3+)) to inhibit the up-regulation of arsenic on the expression of hAS3MT and block arsenic involving in the enzymatic methylation. Moreover, DMPS eliminated arsenic-induced accumulation of ROS, which might contribute to the antidotal effects of DMPS on arsenic posing.

A Tb(III) complex of THP [1,4,7,10-tetrakis(2-hydroxypropyl)-cyclen] (THPTb) cleaved RNA phosphate ester bonds at A-specific sites to mimic RNase U2. The intermediates of the adducts of THPTb2+ and CPP− (cyclic propylene phosphate) or HPNP− (2-hydroxy propyl-p-nitrophenylphosphate) in the hydrolysis of HPNP were directly monitored by electrospray ionization mass spectrometry (ESI-MS).

Amine-functionalized Fe3O4@C nanoparticles have been successfully synthesized on a large scale via a solvothermal route. The morphology, structure and properties of the Fe3O4@C nanoparticles were investigated through different analytical tools. Due to the magnetic nature and the presence of amine-functionalized groups, the as-prepared Fe3O4@C nanoparticles were employed as magnetic carriers for lipase immobilization. Our results indicate that the lipase loading amount on the magnetic Fe3O4@C nanoparticles was about 115.6 mg of protein per g. The factors related to the catalytic activity of the immobilized lipase on the magnetic carriers were systematically investigated. Hydrolytic activity tests reveal that the immobilized lipase retains about 93% of the free enzyme activity. It should be mentioned that the thermal stability of the immobilized lipase was strikingly higher than that of the free lipase. Most importantly, the immobilized lipase retained more than 68% of its initial activities after 10 times reuse. It is hoped that the amine-functionalized Fe3O4@C nanoparticles may find an application in biotechnology and catalysis.

Experimental approach was performed in this paper to study the threshold pressure gradient (TPG) in tight gas reservoir. The nonlinear flow behavior of tight gas reservoir was investigated at first, three zones of flow curve are divided to describe the nonlinear behavior of gas flow in tight formation: solid–gas viscous force zone, slippage zone and low-speed turbulent zone. On this basis, experiments using modified procedure were made in order to clarify the influence of pore pressure on TPG, results show that TPG of tight gas reservoir is highly effected by pore pressure and conventional experimental methods will lead to a significant error. And then, TPG during the development of tight gas reservoir was tested. The results we obtained demonstrated that there exists ‘Dynamic TPG Effect’ during the development process of tight gas reservoir: TPG is increasing along with the decrease of reservoir pressure (pore pressure). New concepts of ‘TPG Rising Cone’ and ‘TPG Sensitivity Coefficient’ are defined to characterize the dynamic TPG of tight gas reservoir. Finally, experiments were carried out to investigate the influence of permeability and water saturation on dynamic TPG. Results indicate that ‘TPG Rising Cone’ is more significant in reservoir with low-permeability or high water saturation.

ianhu ountain, situated southeast of the ibetan lateau, is a key location for testing the role of tectonic uplift in controlling the response of mountain glaciations to climate change in western hi...

The Internet is a typical complex network, whose traffic load is controlled by the inter-domain routing system. Due to the co-location of data plane and control plane of Border Gateway Protocol, the survivability of inter-domain routing system is sensitive to severe congestion. Therefore, an initial outage may lead to a cascade of failures in the Internet. But the cascading failures on links are able to be automatically restored when the congestion is mitigated. In this paper, we propose a model - CAFEIN for characterizing this special process. Based on CAFEIN, we assess the difference of impact under intentional attacks and random breakdowns; identify the worst affected part of the Internet; and study the propagation of cascading failures. Through simulations, we find that the cascading failures bring a great deal of added burden to the routing system. However, the cascading effect is amplified globally when the relative capacity of links is very low. Moreover, the difference of impact between intentional attack and random breakdown is not as prominent as previous research due to the unique automatic-restoration process.

The nucleophilic addition of methanol to two nitrile-functionalized triazamacrocyclic derivatives 1,4,7-tris(cyanomethyl)-1,4,7-triazacyclononane (L1) and 1,4,7-tris(cyanoethyl)-1,4,7-triazacyclononane (L2) were systematically studied under the mediation of various Cd2+ salts with different counter anions. When L1 was reacted with Cd(OAc)2·2H2O in refluxing methanol for 4 h at a ratio of 1:1, complete solvolysis of three pendant CH2CN groups of L1 was achieved and then a trigonal prismatic complex [Cd(L3)]2+ with the resulting imino ether ligand L3 was in situ produced and crystallized upon the addition of stoichiometric NaClO4. After raising the molar ratio of Cd(OAc)2·2H2O/L1 to 1.5:1 or higher and shortening the reaction time to 2 h, L1 was methanolyzed selectively into L5, incorporating two CH2C(OMe) NH and one CH2CN pendant arms because an acetate can still bind to Cd2+ and limits the conversion of the remaining nitrile arm. By adding NaClO4, a mono-capped trigonal prismatic complex [Cd(L5)(OAc)](ClO4) was easily precipitated from the methanolic solution. In contrast to L1, perchlorate, nitrate, and acetate salts of Cd2+ were found to promote the transformation of L2 bearing longer CH2CH2CN pendant arms into the entire solvolysis product L4 after refluxing for 4 h, which utilizes its three CH2CH2C(OMe) NH groups and tacn (tacn = 1,4,7-triazacyclononane) backbone to capture Cd2+ yielding an octahedral complex [Cd(L4)]2+. Additionally, L1 and L2 did not undergo methanolysis when treated with CdCl2·4H2O and two neutral compounds [Cd(L1)Cl2] and [Cd(L2)Cl2]·0.5H2O containing the original nitrile ligands were obtained. The latter was recrystallized from a DMF/CH3CN solution to afford an octahedral solvent-coordinated complex [Cd(L2)(DMF)Cl2]·CH3CN.

Wax crystallization is a serious problem because it may result in the plugging of wellbores, production facilities, and transportation pipelines during oil production. This study describes the use of a novel high-pressure ultrasonic detection system as a reliable technique to evaluate the wax appearance temperature (WAT) and the wax precipitated curve (WPC) of both crude oil [stock tank oil (STO)] and live oil at pressures up to 22.87 MPa. The oil sample was from Kingfisher (KF) oilfield, which is a typical high waxy reservoir. Transit time and amplitude were demonstrated to be good indicators for WAT determination with the ultrasonic method, which could not only self-verify but also distinguish the different stages of the complex process of wax crystallization. In addition, differential scanning calorimetry (DSC) and the rheometry method under ambient pressure were also presented to match the ultrasonic method. The obtained WAT data are comparable to results from DSC and rheometry, which could be used to...

The Shilu Fe-Co-Cu ore district is situated in the western Hainan Province of south China. This district consists of the upper Fe-rich layers and the lower Co-Cu ores, which are mainly hosted within the Neoproterozoic Shilu Group, a dominantly submarine siliciclastic and carbonate sedimentary succession that generally has been metamorphosed to greenschist facies. Three facies of metamorphosed BIFs, the oxide, the silicate-oxide and the sulfide-carbonate-silicate, have been identified within the Shilu Group. The oxide banded iron formation (BIF) fades (quartz itabirites or Fe-rich ores) consists of alternating hematite-rich and quartz-rich microbands. The silicate-oxide BIF facies (amphibolitic itabirites or Fe-poor ores) comprises alternating millimeter to tens of meter scale, magnetite-hematite-rich bands with calc-silicate-rich macro- to microbands. The sulfide-carbonate-silicate BIF facies (Co-Cu ores) contain alternating cobaltiferous pyrite, cobaltiferous pyrrhotite and chalcopyrite macrobands to microbands mainly with dolomite-calcite, but also with minor sericite-quartz bands. Blasto-oolitic, pelletoidal, colloidal, psammitic, and ayptoaystalline to microaystalline textures, and blasto-bedding structures, which likely represent primary sedimentation, are often observed in the Shilu BIF facies. The Shilu BIFs and interbedded host rocks are generally characterized by relatively low but variable Sigma REE concentrations, LREE depletion and/or MREE enrichment relative to HREE, and no Ce, Gd and Eu anomalies to strongly positive Ce, Gd and Eu anomalies in the upward-convex PAAS-normalized REY patterns, except for both the banded or impure dolostones with nil Ce anomaly to negative Ce anomalies and negative La anomalies, and the minor sulfide-carbonate-silicate BIF facies with moderately negative Eu anomalies. They also contain relatively low but variable HFSE abundances as Zr, Nb, Hf, Th and Ti, and relatively high but variable abundances of Cu, Co, Ni, Pb, As, Mn and Ba. The consistently negative epsilon(Nd)(t) values range from -4.8 to -8.5, with a T-DM age of ca. 2.0 Ga. In line with the covariations between Al2O3 and TiO2, Fe2O3 + FeO and SiO2, Mn and Fe, Zr and Y/Ho and REE, and Sc and LREE, the geochemical and Sm-Nd isotopic features suggest that the precursors to the Shilu BIFs formed from a source dominated by seafloor-derived, high- to low temperature, acidic and reducing hydrothermal fluids but with variable input of detrital components in a seawater environment. Moreover, the involved detrital materials were sourced dominantly from an unknown, Paleoproterozoic or older crust, with lesser involvement from the Paleo- to Mesoproterozoic Baoban Group underlying the Shilu Group. The Shilu BIFs of various fades are interpreted to have formed in a shallow marine, restricted or sheltered basin near the rifted continental margin most likely associated with the break-up of Rodinia as the result of mantle superplume activity in South China. The seafloor-derived, periodically upwelling metalliferous hydrothermal plume/vent fluids under anoxic but sulfidic to anoxic but Fe2+-rich conditions were removed from the plume/ vent and accumulated in the basin, and then variably mixed with terrigenous detrital components, which finally led to rhythmic deposition of the Shilu BIFs. (C) 2013 Elsevier B.V. All rights reserved.

Fe3O4 rhombic dodecahedrons with only {110} facets exposed and nanodiscs bounded entirely by {111} facets were fabricated via a one-pot hydrothermal approach. The morphologies, structures and magnetic properties of the rhombic dodecahedrons and nanodiscs were investigated through different analytical tools. Batch experiments indicated that the reaction temperature and amount of N2H4·H2O play important roles in determining the sizes and morphologies of the products. Magnetic analysis revealed that the magnetic properties are closely related to the morphologies of the magnetites. The synthesized Fe3O4 nanocrystals are hoped to have important applications in advanced magnetic materials and catalytic fields.

Cubic phase NH4Eu3F10 nanospheres with controllable sizes were synthesized via a modified hydrothermal route by varying the dosage of ammonium hydroxide solution. Dependence of structure and morphology on the dosage of ammonia water and reaction time were investigated by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). Being unstable, NH4Eu3F10 decomposed into EuF3 and NH4F during the long-time hydrothermal treatment. EDTA, as the chelation agent of Eu3+ and the capping ligand on the surface of as-obtained nanospheres, showed different chelating abilities depending on the dosage of ammonium hydroxide solution. Increasing the amount of ammonia not only decreased the effective concentration of Eu3+, but also decelerated the growth of NH4Eu3F10 nanospheres and stabilized them by reducing the surface energy. Given the satisfactory hydrophilicity, biocompatibility, and luminescence, the as-obtained nanospheres were applied as promising agents for cell imaging by presenting high contrast.

Summary: To maintain proper locomotive patterns, animals constantly monitor body posture with their proprioceptive receptors. In Drosophila, the chordotonal organs (Cho) are especially important in the regulation of locomotion pattern. However, how Cho neurons that are normally activated with sound (vibration) transduce static displacement caused by body position change remains unclear. Here, we report that piezo-like (pzl), a homolog for mammalian piezo1 and 2, is essential for Cho’s function in locomotion. The mutant allele of pzl showed severe defects in crawling pattern and body gesture control, which were rescued by expressing Pzl specifically in Cho neurons. The ability of Cho neurons to respond to micrometer-scale body wall displacement requires pzl. Intriguingly, human or mouse Piezo1 can rescue pzl-mutant phenotypes, suggesting a conserved role of the Piezo-family proteins in locomotion. : Proprioception is critical for animals to maintain body postures and locomotive patterns. Hu et al. find that Drosophila piezo-like (pzl), a putative mechanosensitive channel gene and a homolog for mammalian piezo1 and 2, functions in the stretch-sensing proprioceptive chordotonal neurons to regulate Drosophila larval locomotion. Keywords: mechanotransduction, piezo family, proprioception, chordotonal neurons, locomotion, Drosophila

A class of hydrophilic, photostable, biocompatiable, and highly fluorescent streptavidin-functionalized silica nanoparticles were developed, in which Rhodamine B isothiocyanate molecules were covalently embedded by using Stober method. The silica nanoparticles were ∼60 nm in size and had average fluorescence intensity 4000 times higher than dye molecules. To reduce the severe aggregation, silica nanoparticles were modified with amino groups on the surface by adding (3-aminopropyl)triethoxysilane together with methylphosphonate groups using 3-trihydroxysilylpropylmethylphosphonate, followed by functionalization with streptavidin. The resulting streptavidin-functionalized silica nanoparticles were used for the detection of by reverse-phase protein microarrays based on classical linkage system constituted by biotin-streptavidin conjugation. The calibration curve was linear over the range from 40 amol to 640 amol and the limit of detection was 10 amol, which was 8 times lower than that of streptavidin-labeled cyanine fluorescent dyes. This promising technology may be potential applied for multiplexed signaling and bioassays.

We prepared eight mutants (D76P, D76N, D84P, D84N, D102P, D102N, D150P and D150N) to investigate the functions of residues Asp76, 84, 102 and 150 in human arsenic(III) methyltransferase (hAS3MT) interacting with the S-adenosylmethionine (SAM)-binding. The affinity of all the mutants for SAM were weakened. All the mutants except for D150N completely lost their methylation activities. Residues Asp76, 84, 102 and 150 greatly influenced hAS3MT catalytic activity via affecting SAM-binding or methyl transfer. Asp76 and 84 were located in the SAM-binding pocket, and Asp102 significantly affected SAM-binding via forming hydrogen bonds with SAM.

Submarine surfacing in waves is three dimensional unsteady motion and includes complex coupling between force and motion. This paper uses computational fluid dynamics (CFD) to solve RANS equation with coupled six degrees of freedom solid body motion equations. RANS equations are solved by finite difference method and PISO arithmetic. Level-set method is used to simulate the free surface. Computations were performed for the standard DARPA SUBOFF model. The structured dynamic overset grid is applied to the numerical simulation of submarine surfacing (no forward speed) in regular waves and computation cases include surfacing in the calm water, transverse regular waves with different ratio of wave height and submarine length (h/L = 0.01, 0.02, 0.03, 0.04) and transverse regular waves with different ratio of wave length and submarine length (λ/L = 0.5, 1, 1.5). The asymmetric vortices in the process of submarine surfacing can be captured. It proves that roll instability is caused by the destabilizing hydrodynamic rolling moment overcoming the static righting moment both under the water and in regular waves. Relations among maximum roll angle, surfacing velocity fluctuation and wave parameters are concluded by comparison with variation trend of submarine motion attitude and velocity of surfacing in different wave conditions. Simulation results confirm that wave height h/L = 0.04 and wave length λ/L = 1.5 lead to surfacing velocity fluctuation significantly. Maximum roll angle increases with the increase of wave height and wave length. Especially the law presents approximate linear relationship. Maximum roll angle with wave height (h/L = 0.04) can reach to 7.29° while maximum roll angle with wave length (λ/L = 1.5) can reach to 5.79° by contrast with 0.85° in calm water. According to the above conclusions, maneuverability can be guided in the process of submarine surfacing in waves in order to avoid potential safety hazard.

Lysosomes in astrocytes and microglia can release ATP as the signaling molecule for the cells through ca(2+)-dependent exocytosis in response to various stimuli. At present, fluorescent probes that can detect ATP in lysosomes have not been reported. In this work, we have developed a new water-soluble cationic polythiophene derivative that can be specifically localized in lysosomes and can be utilized as a fluorescent probe to sense ATP in cells. PEMTEI exhibits high selectivity and sensitivity to ATP at physiological pH values and the detection limit of ATP is as low as 10(-11)M. The probe has low cytotoxicity, good permeability and high photostability in living cells and has been applied successfully to real-time monitoring of the change in concentrations of ATP in lysosomes though fluorescence microscopy. We also demonstrated that lysosomes in Hela cells can release ATP through Ca(2+)-dependent exocytosis in response to drug stimuli.

In the human body, arsenic is metabolized by methylation. Understanding this process is important and provides insight into the relationship between arsenic and its related diseases. We used the rapid equilibrium kinetic model to study the reaction sequence of arsenite methylation. The results suggest that the mechanism for arsenite methylation is a completely ordered mechanism that is also of general interest in reaction systems with different reductants, such as tris(2-carboxyethyl)phosphine, cysteine, and glutathione. In the reaction, cysteine residues of recombinant human arsenic (+3 oxidation state) methyltransferase (hAS3MT) coordinate with arsenicals and involve the methyl transfer step. S-Adenosyl-l-methionine (AdoMet) is the first-order reactant, which modulates the conformation of hAS3MT to a best matched state by hydrophobic interaction. As the second-order reactant, reductant reduces the disulfide bond, most likely between Cys-250 and another cysteine residue of hAS3MT, and exposes the active site cysteine residues for binding trivalent inorganic arsenic (iAs(3+)) to give monomethylarsonic dicysteine (MADC(3+)). In addition, the reaction can be extended to further methylate MADC(3+) to dimethylarsinic cysteine (DAMC(3+)). In the methylation reaction, the β-pleated sheet content of hAS3MT is increased, and the hydrophobicity of the microenvironment around the active sites is decreased. Similarly, we confirm that both the high β-pleated sheet content of hAS3MT and the high dissociation ability of the enzyme-AdoMet-reductant improve the yield of dimethylated arsenicals.

Hierarchically micro-/nanostructured coordination polymer [Cu(2,5-PDC)H2O]n architectures with tunable morphologies have been successfully prepared by rationally adjusting the preparation parameters, such as the reactant concentration, solvent, surfactant, and reaction temperature. Using simple calcinations of chosen shaped [Cu(2,5-PDC)H2O]n architectures, we can obtain several porous copper-based inorganic motifs, which show potential applications for the antibacterial field and lithium ion batteries. Therein, CuO-1 can kill the Gram-positive bacteria Bacillus subtilis and Staphylococcus aureus better than other materials. The value for initial discharge capacity of CuO-3 (1160 mAh g–1) is higher than the theoretical capacity (674 mAh g–1) and most copper oxide materials. Besides, Cu/C composites also show intense application in the antibacterial and Li-ions uptake-release field, which will provide a widely used method to prepare the nanosystem of carbon-coating or carbon-compositing materials by simple ...

A novel pyridine containing tetraazamacrocycle 3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene-3,6,9-triacetic acid ethyl ester (1) and its mononuclear Mn2+ complex (2) have been prepared. Pyridine induced the π–π stacking of [Mn1]2+ and provided donors for nonclassical C H…O hydrogen bonding as well. In the solid state of 2, the combination of π–π interactions and hydrogen bonding constructed a 3D crystal structure and thus formed pairs of interacting mononuclear complexes that mediated weak magnetic exchanges between the Mn2+ ions. Meanwhile, self-assembly of 2 dissociated in the aqueous solution, and the effect of pyridine on the nature of DNA binding with 2 have also been investigated.

Spheres-like coordination polymer architectures in submicro regimes have been synthesized from the hydrothermal reaction of transition metal ions and 3,5-bis(pyridin-3-ylmethylamino)benzoic acid (L...

Isolated NE-SW stretching the Helan Mountain massif, separating the temperate grassland of the Ordos plateau from the Tenggeli Desert, is a key position of studying the glacier development in west China as well as the coupling conditions of climate change with tectonic uplift. The glacial landforms and deposits including cirques, peaks, knife-edge ridges, lateral moraines, and terminal moraines distribute above 2800 m a.s.l. in the middle part of the Helan Mountain. This distribution indicates that here was once glaciated during the late Quaternary. Morphology features show a clear sequence of landscape forming events took place throughout the Helan Mountain. Laboratory optically stimulated luminescence (OSL) and accelerator mass spectrometry radiocarbon dating (AMS 14C) results indicate a late history of glacial advance. Late Pleistocene glaciers in the middle part of the Helan Mountain advanced to near their positions at least four times, and the glacial sequences can be assigned as the middle stage of last glacial cycle (MIS3b, 43.2±4.0 ka), last glacial maximum (LGM, ∼18 ka), late glacial (12.0±1.1 ka) and neo-glacial (3.4±0.3 ka) respectively. Adopting equilibrium line altitude ∼2980 m of last glacial maximum and the modern theoretical snowline altitude ∼4724 m as the maximum amplitudes, and the standard marine isotope curve (MIS) as the glacial equilibrium line change since the Gonghe Movement (150 ka), the relationship between the mountain altitude and glacier development is discussed herein. Compared with other environmental indexes such as the loess-paleosol and ice core, conclusions are made that glacier advances in the Helan Mountain during the late Quaternary obviously depended on the coupled control of tectonic uplift of mountain with the climate condition. It is at last glaciation that the mountain reached the altitude above snowline and coupled with the glacial climate. The glacial advances occurred in the early and middle stages of last glacial cycle after the Gonghe Movement.

The stable dinuclear [Cu(μ-C2O4)Cu]2+ entity is facially coordinated at each end by a N-nitrile functionalized triazamacrocycle, 1, 4, 7-tris(cyanomethyl)-1, 4, 7-triazacyclononane (L), to generate a centrosymmetric compound [Cu2L2(μ-C2O4)](ClO4)2·4DMF (1) containing a bis-bidentate oxalate bridge. The variable-temperature magnetic measurement for the crystallographically characterized compound exhibits quite strong antiferromagnetic coupling interaction between two oxalate-linked CuII atoms separated by 5.149 A with a singlet-triplet energy gap of –345.5 cm–1. On the other hand, a mononuclear CoIII compound [CoL(N3)3]·2.5H2O (2) with monodentate azide terminal groups was synthesized. Structural elucidation by X-ray diffraction shows that the compound has crystallographically imposed C3 symmetry. Enantiomerically pure crystals were obtained upon crystallization indicated by a Flack parameter of 0.04(5).

Self-assembly between perchlorate salts of Cu(II), Zn(II) and Cd(II) with tri-substituted N-propionic acid functionalized 1,4,7-triazacyclononane (H33L11) or the mono-substituted one (HL22) results in the formation of four novel complexes [Cu5(H2O)6(L11)2](ClO4)4 (1), [Zn9(L11)4(H2O)18](ClO4)6·9H2O (2), [Cd2(H22L11)2](ClO4)2 (3) and [Cd(L22)]ClO4·CH3OH (4) with different aggregation modes. All these complexes were structurally characterized by solid state X-ray diffraction measurement. Complex 1 belongs to a homometallic 2D polymer, where each [Cu(L11)]− complex entity acts as a three-connected node joined to three Cu(II) ions through μ2 bridged propionate arms to afford a puckered honeycomb framework. In complex 2, two face-to-face arranged [Zn(L11)]− moieties clip three Zn(II) ions by virtue of pendant propionate arms generating a macrotricyclic metallacryptate. Two such metallacryptates are fused via co-sharing one lateral Zn(II) ion into an unprecedented nonazinc cluster with a double-cage architecture. Complex 3 exhibits a discrete centrosymmetric dinuclear unit [Cd2(H22L11)2]2+ consisting of two pendant propionate groups linked to a [Cd2O2] core. Complex 4 reveals Cd(II) centers are associated through the unique propionate bridge of the L22− ligand leading to an infinite 1D zig–zag polymeric chain of [Cd(L22)]+ cations. Deduced from the structural investigations, the linkage patterns of the selected macrocyclic ligands towards metal centers may be exquisitely tuned according to the type of metals and the number of the coordinating pendant arms present in the macrocyclic ligands, and then the architectural variation of these metal–organic coordination species is achieved. In addition, magnetic studies for complex 1 show a weak Cu⋯Cu antiferromagnetic coupling in the 2D honeycomb layer with a Weiss temperature of −4.31 K.

A novel fluorescent sensor composed of a naphthalene functionalized tetraazamacrocycle ligand 3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene-3-methyl naphthalene (1) and Zn(2+) has been designed and prepared, which can be utilized for selective and ratiometric sensing of pyrophosphate (PPi) over other phosphate-containing anions in aqueous solution at physiological pH. Notably, the water soluble 1 itself also exhibits a selective enhanced fluorescent response to Zn(2+), and the complex 1-Zn(2+) thus formed eventually fulfils the synergic Zn(2+) coordination-altered strategy with PPi. Furthermore, the ratiometric sensing of 1-Zn(2+) towards PPi performed well even in blood serum milieu. Finally, the sensor 1-Zn(2+) was successfully employed to monitor a real-time assay of inorganic pyrophosphatase (PPase) by means of ratiometric fluorescent measurements for the first time.

The catalytic mechanism of the recombinant human arsenic (+3) methyltransferase (hAS3MT) was studied using kinetics, initial velocity and spectroscopy. The production and the distribution of methylated arsenicals changed with various concentrations of arsenite/S-adenosyl-L-methionine (SAM)/thiols, enzyme contents, and incubation times. These results suggest a sequential methylation of arsenite to monomethylated arsenicals (MMA) and dimethylated arsenicals (DMA). In addition, competition exists between the two reactions. hAS3MT showed the greatest activity at pH 8.5 with glutathione (GSH) as the reductant. This might indicate that a balance between the deprotonation and protonation of sulfhydryl groups is required. Initial velocity studies illuminate an ordered sequence for the binding of SAM and arsenite to the hAS3MT; while GSH should probably be placed either as the first reactant or as a reactant combining with the enzyme only after products have been released. The interactions between substrate/cofactors and the hAS3MT were first monitored by UV-visible and circular dichroism spectroscopy. It revealed that arsenite and SAM combined with the hAS3MT before reaction started; whereas, no interactions between GSH and the hAS3MT were detected. Integrating the results from kinetics, initial velocity and spectroscopy studies, an ordered mechanism are originally attained, with the SAM as the first reactant that adds to the hAS3MT and arsenite as the second one. Arsenite is successively methylated reductively, rather than a stepwise oxidative methylation. GSH should combine with the hAS3MT after the methylation to reduce the disulfide bond formed during the catalytic cycle in the hAS3MT to resume the active form of the enzyme.

Phytotoxic effects of phenolic compounds have been extensively studied, but less attention has been given to the effects of these compounds on soil microbial communities, which are crucial to the productivity of agricultural systems. Responses of cucumber rhizosphere bacterial and fungal communities to syringic acid (SA), a phenolic compound with autotoxicity to cucumber, were analyzed by high-throughput sequencing of 16S rRNA gene and internal transcribed spacer amplicons. SA at the concentration of 0.1 μmol g-1 soil changed rhizosphere bacterial and fungal community compositions, decreased bacterial community diversity but increased fungal community richness and diversity (P

Three novel transition metal complexes with 1,4,7-tris(cyanomethyl)-1,4,7-triazacyclononane (L) were synthesized and structurally characterized. In complex [FeLCl3]·2H2O (1), three N-donors from the macrocyclic backbone and three chloride anions complete the coordination polyhedron around Fe(III) and lead to a neutral [FeLCl3] unit. The neutral Fe(III) units of the same chirality are linked through weak interactions into 3D supramolecular network with hexagonal channels. Guest water molecules trapped inside the channel are associated into an unprecedented 1D linear chain. The crystal structures of complexes [NiL(CH3CN)3](ClO4)2·0.5H2O (2) and [CdL(CH3CN)3](ClO4)2·0.5H2O (3) reveal that the metal center lies in a distorted octahedral N6 environment with three acetonitrile occupying the remaining coordination sites opposite to the macrocyclic ring. The artificial nuclease activity of redox-active complex 1 towards pMD–AMT plasmid DNA was assessed by gel electrophoresis. As a result, complex 1 can effectively cleave supercoiled DNA under near physiological conditions with/without H2O2 in a time- and complex concentration-dependent manner.

A simple method for the preparation of core-shell micro/nanostructured magnetic molecularly imprinted polymers (MIPs) for protein recognition is described. Magnetic MIPs were synthesized by copolymering gamma-aminopropyltrimethoxysilane and tetraethyl orthosilicate at the surface of Fe(3)O(4) nanospheres, which were directly covalently bound with template molecule, bovine hemoglobin (BHb), through imine bond. Transmission electron microscopy and scanning electron microscopy images showed that the Fe(3)O(4) nanospheres with diameter about 50-150 nm were coated with the MIPs layer with average thickness about 10 nm, which enabled the magnetic MIPs to have a sensitive and fast magnetic response. The proximity between the thickness of MIPs layer and the spatial size of BHb indicated that the imprinted sites almost situated at the surface of magnetic MIPs, leading a rapid adsorption saturation within 1 h. And the adsorption amounts of magnetic MIPs toward BHb were estimated to be 10.52 mg/g at pH 6.5, which was 4.6 times higher than that of magnetic nonmolecularly imprinted polymers. Meanwhile, the result of selective test showed that the magnetic MIPs had an excellent recognition capacity to BHb compared to the other nontemplate proteins. Except for the spatial size complementary between BHb and the binding sites in magnetic MIPs, the electrostatic interaction also was proven to be an important factor for recognizing the imprinting molecule.

Core-shell structural molecularly imprinted polymer (Cs-MIP) has been successfully prepared by polymerization of MIP on the silica nanospheres surface. The vinyl groups modified on the surface of silica nanospheres have directed the copolymerization of functional monomers and cross linkers in the presence of template molecule, hydroquinone, onto the silica nanospheres surface. The prepared Cs-MIP exhibited fast binding kinetics because the rebinding sites situated at the surface and approximately to the surface of the outer MIP layer. And the Cs-MIP showed higher recognition capacity to hydroquinone than to analogous compounds, such as catechol and resorcinol. An electrochemical sensor fabricated by modifying Cs-MIP on the glassy carbon electrode surface was employed to detect the concentration of hydroquinone with a linear range from 2.0 x 10(-6) to 1.0 x 10(-4) mol/L.

The effects of Se(IV) on the structure and function of recombinant human arsenic (+3 oxidation state) methyltransferase (AS3MT) purified from the cytoplasm of Escherichia coli were studied. The coding region of human AS3MT complementary DNA was amplified from total RNA extracted from HepG2 cell by reverse transcription PCR. Soluble and active human AS3MT was expressed in the E. coli with a Trx fusion tag under a lower induction temperature of 25 degrees C. Spectra (UV-vis, circular dichroism, and fluorescence) were first used to probe the interaction of Se(IV) and recombinant human AS3MT and the structure-function relationship of the enzyme. The recombinant human AS3MT had a secondary structure of 29.0% alpha-helix, 23.9% beta-pleated sheet, 17.9% beta-turn, and 29.2% random coil. When Se(IV) was added, the content of the alpha-helix did not change, but that of the beta-pleated sheet increased remarkably in the conformation of recombinant human AS3MT. Se(IV) inhibited the enzymatic methylation of inorganic As(III) in a concentration-dependent manner. The IC(50) value for Se(IV) was 2.38 muM. Double-reciprocal (1/V vs. 1/[inorganic As(III)]) plots showed Se(IV) to be a noncompetitive inhibitor of the methylation of inorganic As(III) by recombinant human AS3MT with a K (i) value of 2.61 muM. We hypothesized that Se(IV) interacts with the sulfhydryl group of cysteine(s) in the structural residues rather than the cysteines of the active site (Cys156 and Cys206). When Se(IV) was combined with cysteine(s) in the structural residues, the conformation of recombinant human AS3MT changed and the enzymatic activity decreased. Considering the quenching of tryptophan fluorescence, Cys72 and/or Cys226 are deduced to be primary targets for Se(IV).

A one-step precipitation polymerization synthesis was adopted for the preparation of molecularly imprinted polymers (MIPs) by using hydroquinone as a template molecule. The transmission electron microscopy (TEM) exhibited that the polymers were uniform spheres with the diameter of about 700 nm. The results of adsorption experiments showed that the microspherical imprinted polymers possessed fast adsorption dynamics. Compared to the structurally similar compounds, catechol and resorcinol, the MIPs exhibited a high recognizable capacity to hydroquinone. And the electrochemical sensor fabricated by modifying the prepared MIPs microsphere on the glassy carbon electrode surface was used to detect the hydroquinone concentration. The current response was proportional to the concentration of hydroquinone in the range of 2.0 × 10 −6 to 1.0 × 10 −4 mol/L with the detection limit of 1.0 × 10 −6 mol/L.

A novel composite of multiwalled carbon nanotubes (MWNTs) and molecularly imprinted polymers (MIPs) was prepared by using dopamine (DA) as a template molecule. Selective copolymerization of methacrylic acid and trimethylolpropane trimethacrylate (copoly(MAA-co-TRIM)) in the presence of DA was achieved at the vinyl group functionalized MWNT surface. Vinyl groups modified on MWNTs surface are a key factor for the formation the composite of MWNTs-MIPs. Attenuated total reflection Fourier transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, and thermogravimetric analysis were used to characterize the composite structure and determine the grafted MIPs quantities in the composite. The properties such as adsorption dynamics, special binding, and selective recognition capacity were evaluated. The results demonstrated that MWNTs-MIPs not only possessed a rapid dynamic adsorption but also exhibited a high selectivity toward DA, compared to epinephrine. The electrochemical...

Copper(II) complex with a new ligand 1,4,7-tris(carbamoylethyl)-1,4,7-triazacyclononane (L) has been synthesized and characterized by elemental analysis, FT-IR, ES-MS, UV–Vis and cyclic voltammetry. Determined by X-ray analysis, the crystal structure shows the metal center is six-coordinated. The compound can catalyze the oxygenation of ethyl phenyl sulfide (EPS) utilizing H2O2 under ambient conditions. EPS was converted to the corresponding sulfoxide and sulfone step by step which was confirmed by 1H NMR spectra. The existence of sulfoxide and sulfone was identified by GC–MS. The gradually disappearance of EPS’s ultraviolet absorption at 290 nm was significantly correlated with the rates of sulfide consumption. The initial reaction rate during the first 3 h is consistent with the first-order law in substrate concentration. The averaged pseudo-first-order rate constant is calculated to be (2.25 ± 0.42) × 10−3 min−1 at 25 °C and (4.44 ± 0.17) × 10−3 min−1 at 30 °C. The oxidation product is almost sulfoxide by choosing the molar concentrations of Cu complex (2% of substrate) and H2O2 (seven times as much as substrate).

Complexes of N,N′,N′′-tris(2-hydroxypropyl)-1,4,7-triazacyclononane (L), [CuL](ClO4)(NO3) (1), [CoL](ClO4)2 (2), [ZnL](ClO4)2 (3) and [MnL](ClO4)2 (4), have been synthesized and characterized on the basis of elemental analysis, electrospray ionization mass spectrometry, UV–Vis measurements and cyclic voltammetry. Crystal structures of the former three complexes, characterized by X-ray crystallography, show that these complexes are monoclinic with space group P21/n and P21/c. Each metal central in the complexes is six-coordinate with three N atoms of the macrocycle and three O atoms from the pendant hydroxypropyl arms, forming a distorted octahedral configuration. [MnL](ClO4)2 (4) is employed as catalyst in olefin epoxidation with H2O2. The final results indicate that complex (4) has good catalytic activity towards olefin epoxidation. Under mild conditions, the olefin conversion is moderate and epoxidation selectivity is 95–100%.

In order to solve the integrated condition monitoring problem in space information network, there are three works finished including analyzing the characteristics of tasks process and system health monitoring, adopting the automata modeling method, and respectively establishing the models for state inference and state determination. The state inference model is a logic automaton and is gotten by concluding engineering experiences. The state determination model is a double-layer automaton, the lower automaton is responsible for parameter judge and the upper automaton is responsible for state diagnosis. At last, the system state monitoring algorithm has been proposed, which realizes the integrated condition monitoring for task process and system health, and can avoid the false alarm.

The characteristic of satellite communication link was firstly described and four application modes were put forward. By comparison, it is suggested that microwave link is used in satellite-to-ground communication and laser link is used in inter-satellite communication. Secondly the condition and composition of laser link establishment was analyzed and laser link model was set up, and the principle and composition of APT system was described. Finally, based on STK and MATLAB platform, the process of inter-satellite laser link establishment was designed, and setting the scene of TDRS capturing and tracking user’s satellite as an example, simulation was realized and demonstrated.

Toxoplasma gondii is an obligate intracellular apicomplexan parasite, and can infect warmblooded animals and humans all over the world. In the past years, ROP family genes encoding particular proteins of T. gondii had made a great contribution to toxoplasmosis. In this study, we used multiple bioinformatics approaches to predict the physical and chemical characteristics, transmembrane domain, epitope, and topological structure of the rhoptry protein 48 (ROP48). The results indicated that ROP48 protein was mainly located in the membrane and had several positive linear-B cell epitopes and Th-cell epitopes, which suggested that ROP48 is a potential DNA vaccine candidate against toxoplasmosis. Then the PCR product amplified from the ROP48 cDNA was inserted into a pEASY-T1 vector to build a recombinant cloning plasmid. After sequencing, ROP48 was subcloned into a eukaryotic expression plasmid pEGFP-C1 to obtain pEGFP-C1-ROP48 (pROP48). After identification by PCR and restriction enzyme digestion, the recombinant plasmid pROP48 was transfected into HEK 293-T cell and identified by RT-PCR. The results showed that the eukaryotic expression plasmid pROP48 was constructed and transfected to the cells of HEK 293-T successfully. Western blotting showed that the expressed proteins can be recognized by anti-STAg mouse sera.

Since arsenic trioxide (As3+) has been successfully used in the treatment of acute promyelocytic leukemia (APL), its adverse effects on patients have been problematic and required a solution. Considering the good therapeutic potency and low toxicity of tetraarsenictetrasulfide (As4S4) in the treatment of APL, we investigated the effects of combining As4S4 and As3+ on the apoptosis and differentiation of NB4 and primary APL cells. As4S4, acting similarly to As3+, arrested the G1/S transition, induced the accumulation of cellular reactive oxygen species, and promoted apoptosis. Additionally, low concentrations of As4S4 (0.1-0.4 μM) induced differentiation of NB4 and primary APL cells. Compared with the As4S4- or As3+-treated groups, the combination of As4S4 and As3+ obviously promoted apoptosis and differentiation of NB4 and primary APL cells. Mechanistic studies suggested that As4S4 acted synergistically with As3+ to down-regulate Bcl-2 and nuclear factor-κB expression, up-regulate Bax and p53 expression, and induce activation of caspase-12 and caspase-3. Moreover, the combination of low concentrations of As4S4 and As3+ enhanced degradation of the promyelocytic leukemia-retinoic acid receptor α oncoprotein. In summary, As4S4 and As3+ synergistically induce the apoptosis and differentiation of NB4 and primary APL cells.

Considering the significant role of plasma homocysteine in physiological processes, two ensembles (F465-Cu(2+) and F508-Cu(2+)) were constructed based on a BODIPY (4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene) scaffold conjugated with an azamacrocyclic (1,4,7-triazacyclononane and 1,4,7,10-tetraazacyclododecane) Cu(2+) complex. The results of this effort demonstrated that the F465-Cu(2+) ensemble could be employed to detect homocysteine in the presence of other biologically relevant species, including cysteine and glutathione, under physiological conditions with high selectivity and sensitivity in the turn-on fluorescence mode, while the F508-Cu(2+) ensemble showed no fluorescence responses toward biothiols. A possible mechanism for this homocysteine-specific specificity involving the formation of a homocysteine-induced six-membered ring sandwich structure was proposed and confirmed for the first time by time-dependent fluorescence spectra, ESI-MS and EPR. The detection limit of homocysteine in deproteinized human serum was calculated to be 241.4 nM with a linear range of 0-90.0 μM and the detection limit of F465 for Cu(2+) is 74.7 nM with a linear range of 0-6.0 μM (F508, 80.2 nM, 0-7.0 μM). We have demonstrated the application of the F465-Cu(2+) ensemble for detecting homocysteine in human serum and monitoring the activity of cystathionine β-synthase in vitro.

A novel 1D polymer [Cu 3 (μ 3 -OH) 2 (μ 2 –H 2 O) 2 (H 2 O) 2 (Agly) 2 ]·(ClO 4 ) 2 was synthesized through the self-assembly of Cu 2+ and acetylglycine (Agly) in aqueous solution and characterized by X-ray structure analysis. The compound crystallizes in the monoclinic P 2(1)/ c space group ( a =5.4762(1) A, b =15.6136(1) A, c =13.9036(5) A, β =98.584(1)°, Z =2) and represents the first 1D coordination polymer with tetranuclear rhombus-like [Cu 4 O 4 ] unit as building block. It should be noted that the rhombus are sharing two vertices and the structure can also be viewed as a zigzag chain based on [Cu 3 ] building blocks. Agly ligand adopts η 2 -coordinated mode and is used to connect two copper ions. With the help of hydrogen bonds, the 1D chains are further linked into ‘∞’ like channels in which counter-anions ClO 4 − are located. The magnetic susceptibility measurements (1.8–300 K) agree with a moderately strong antiferromagnetic interaction between the Cu centers with a J value of −40(2) cm −1 .

The triazamacrocyclic ligand L functionalized with nitrile pendant arms undergoes metal-promoted hydrolysis in undried CH3CN to afford amide derivative L1 followed by the formation of a complex [ZnL1](ClO4)2 (1), which was structurally characterized. Furthermore, unexpected metal-assisted decyanomethylation reaction of the ligand L was observed via electrospray ionization mass spectrum (ESI-MS) when aqueous CH3CN was employed as the reaction solvent.

The electrochemical behavior of Cu2Zn2SOD on mercury electrodes was studied by controlled potential electrolysis. By comparison of UV, Raman spectra and activity of Cu2Zn2SOD before electrochemical reduction and after re-oxidation, it is proved that the conformation and activity are not changed.

The electrochemical behavior of bovine erythrocyte superoxide dismutase (BESOD) on a hanging or dropping mercury electrode was studied by cyclic voltammetry (CV) and normal pulse polarography (NPP). Two defined peaks in CV or in NPP diagrams were attributed to the peaks of copper(II) and zinc(II), respectively. The electrode processes were irreversible and possessed an adsorptive characteristic. The adsorption of BESOD was estimated by double potential-step chronocoulometry. The average area of each molecule of absorbed BESOD was obtained, which is in good agreement with that determined by X-ray structure analysis. The diffusion coefficients were determined by NPP and double potential-step chronocoulometry, being in agreement with each other. The experimental results confirm that in the absence of a promotor or mediator, mercury electrodes are feasible for the investigation of BESOD.

Single domain bulk YBa1.8K0.2Cu3Oy+0.4Y2BaCuO5 (MTG-YBKCO) has been successfully prepared by melt-textured growth. The curve of critical current density versus applied magnetic field at 55 K shows a peak at around 3.5 T. Jc of greater than 7×104 A/cm2 is observed over a broad range of 0–6 T. The peak disappears at temperatures higher than 70 K.

A new heterodinuclear cryptate [AgCuL](ClO4−)2 was synthesized by transmetallation via its precursor [Ag2L](ClO4−)2 (L = ligand). The electrospray mass spectrum (ES-MS) showed that the heterodinuclear entity exists in the solution. The X-Ray structure analysis shows that the AgI ion has tetrahedral geometry while CuI lies in a three-coordinate environment.