Contributions of phosphatase and microbial activity to internal phosphorus loading and their relation to lake eutrophication

Phosphatase may accelerate the process of lake eutrophication through improving phosphorus bioavailability. This mechanism was studied in three Chinese eutrophic shallow lakes (Lake Taihu, Lake Longyang,and Lake Lianhua). Phosphatase activity was related to the concentration of soluble reactive phosphorus (SRP) and chlorophyll a. Stability of dissolved phosphatase in reverse micelles may be attributed to molecular size, conformation and active residues of the enzyme. At the site with Microcystis bloomed in Lake Taihu, dissolved phosphatase activity was higher and more stable in micelles, SRP concentrations were lower in interstitial water, the contents of different forms of phosphorus and the amounts of aerobic bacteria were lower while respiration efficiency was higher in sediments. Phosphobacteria, both inorganic and organic and other microorganisms were abundant in surface water but rare in sediments. Therefore, internal phosphorus may substantially flux into water column by enzymatic hydrolysis and anaerobic release, together with mobility of bacteria, thereby initiating the bloom. In short, biological mechanism may act in concert with physical and chemical factors to drive the internal phosphorus release and accelerate lake eutrophication.

Raman scattering of non-planar graphite: arched edges, polyhedral crystals, whiskers and cones

Planar graphite has been extensively studied by Raman scattering for years. A comparative Raman study of several different and less common non-planar graphitic materials is given here. New kinds of graphite whiskers and tubular graphite cones (synthetic and natural) have been introduced. Raman spectroscopy has been applied to the characterization of natural graphite crystal edge planes, an individual graphite whisker graphite polyhedral crystals and tubular graphite cones. Almost all of the observed Raman modes were assigned according to the selection rules and the double-resonance Raman mechanism. The polarization properties related to the structural features, the line shape of the first-order dispersive mode and its combination modes, the frequency variation of some modes in different carbon materials and other unique Raman spectral features are discussed here in detail.

Recent advances in synthesis and properties of cubic boron nitride films

Cubic boron nitride (c-BN) attracts widespread interest as a promising material for many potential applications because of its unique physical and chemical properties. Since the 1980's the research in c-BN thin films has been carried out, which reached its summit in the mid of 1990's, then turned into a downward period. In the past few years, however, important progress was achieved in synthesis and properties of cubic boron nitride films, such as obtaining > 1 mu m thick c-BN films, epitaxial growth of single crystalline c-BN films, and advances in mechanics properties and microstructures of the interlayer of c-BN films. The present article reviews the current status of the synthesis and properties of c-BN thin films.

Surface Initiated Polymerization from Substrates of Low Initiator Density and Its Applications in Biosensors

Surface initiated polymerization (SIP) has become an attractive method for tailoring physical and chemical properties of surfaces for a broad range of applications. Most of those application relied on the merit of a high density coating. In this study we explored a long overlooked field of SIP. SIP from substrates of low initiator density. We combined ellipsometry with AFM to investigate the effect of initiatior density and polymerization time on the morphology of polymer coatings. In addition, we carefully adjusted the nanoscale separation of polymer chains to achieve a balance between nonfouling and immobilization capacities. We further tested the performance of those coating on various biosensors, such as quartz crystal microbalance, surface plasmon resonance, and protein microarrays. The optimized matrices enhanced the performance of those biosensors. This report shall encourage researches to explore new frontiers in SIP that go beyond polymer brushes.

Intercellular calcium wave propagation in linear and circuit-like bone cell networks

In the present study, the mechanism of intercellular calcium wave propagation in bone cell networks was identified. By using micro-contact printing and self-assembled monolayer technologies, two types of in vitro bone cell networks were constructed: open-ended linear chains and looped hexagonal networks with precisely controlled intercellular distances. Intracellular calcium responses of the cells were recorded and analysed when a single cell in the network was mechanically stimulated by nano-indentation. The looped cell network was shown to be more efficient than the linear pattern in transferring calcium signals from cell to cell. This phenomenon was further examined by pathway-inhibition studies. Intercellular calcium wave propagation was significantly impeded when extracellular adenosine triphosphate (ATP) in the medium was hydrolysed. Chemical uncoupling of gap junctions, however, did not significantly decrease the transferred distance of the calcium wave in the cell networks. Thus, it is extracellular ATP diffusion, rather than molecular transport through gap junctions, that dominantly mediates the transmission of mechanically elicited intercellular calcium waves in bone cells. The inhibition studies also demonstrated that the mechanical stimulation-induced calcium responses required extracellular calcium influx, whereas the ATP-elicited calcium wave relied on calcium release from the calcium store of the endoplasmic reticulum.

Structure and acidity of Mo/H-MCM-22 catalysts studied by NMR spectroscopy

A comprehensive study on physical and chemical properties of Mo/MCM-22 bifunctional catalysts has been made by using combined analytic and spectroscopic techniques, such as adsorption, elemental analysis, and Xe-129 and P-31 NMR of adsorbed trialkylphosphine oxide probe molecules. Samples prepared by the impregnation method with Mo loadings ranging from 2-10 wt.% have been examined and the results are compared with that obtained from samples prepared by mechanical mixing using MoO3 or Mo2C as agents. Sample calcination treatment is essential in achieving a well-dispersed metal species in Mo/MCM-22. It was found that, upon initial incorporation, the Mo species tend to inactivate both Bronsted and Lewis sites locate predominantly in the supercages rather than the 10-membered ring channels of MCM-22. However, as the Mo loading exceeds 6 wt.%, the excessive Mo species tend to migrate toward extracrystalline surfaces of the catalyst. A consistent decrease in concentrations of acid sites with increasing Mo loading < 6 wt.% was found, especially for those with higher acid strengths. Upon loading of Mo > 6 wt.%, further decreases in both Bronsted and Lewis acidities were observed. These results provide crucial supports for interpreting the peculiar behaviors previously observed during the conversion of methane to benzene over Mo/MCM-22 catalyst under non-oxidative conditions, in which an optimal performance was achieved with a Mo loading of 6 wt.%. The effects of Mo incorporation on porosity and acidity features of the catalyst are discussed. (C) 2004 Published by Elsevier B.V.

Metal nanomaterials and carbon nanotubes - synthesis, functionalization and potential applications towards electrochemistry

This review focuses on the synthesis, assembly, surface functionalization, as well as application of inorganic nanostructures. Electrochemical and wet- chemical methods are demonstrated to be effective approaches to make metal nanostructures under control without addition of a reducing agent or protecting agent. Owing to the unique physical and chemical properties of the nano-sized materials, novel applications are introduced using inorganic nanomaterials, such as electrocatalysis, photoelectricity, spectrochemistry, and analytical chemistry.

A single ionic conductor based on Nafion and its electrochemical properties used as lithium polymer electrolyte

In an attempt to raise the transport number of Li+ to nearly unity in solid polymer electrolytes, commercial perfluorinated sulfonate acid membrane Nafion 117 was lithiated and codissolved with copolymer poly(vinylidene fluoride)hexafluoropropylene. The effect of fumed silica on the physical and electrochemical properties of the single ion conduction polymer electrolyte was studied with atom force microscopy, fourier transform infrared spectroscopy, differential scanning calorimetry, and electrochemical impedance spectroscopy. It was confirmed that the fumed silica has an obvious effect on the morphology of polymer electrolyte membranes and ionic conductivity. The resulting materials exhibit good film formation, solvent-maintaining capability, and dimensional stability. The lithium polymer electrolyte after gelling with a plasticizer shows a high ionic conductivity of 3.18 x 10(-4) S/cm.

Lanthanide complex/polymer composite optical resin with intense narrow band emission, high transparency and good mechanical performance

Novel composite resins possessing good luminescent properties have been synthesized through a free radical copolymerization of styrene, alpha-methylacrylic acid and the binary or ternary complexes of lanthanide ions (Eu3+ and Tb3+). These polymer-based composite resins not only possess good transparency and mechanical performance but also exhibit an intense narrow band emission of lanthanide complexes under UV excitation. We characterized the molecular structure, physical and mechanical performance, and luminescent properties of the composite resins. Spectra investigations indicate that alpha-methyl-acrylic acid act as both solubilizer and ligand. Photoluminescence measurements indicate that the lanthanide complexes show superior emission lines and higher intensities in the resin matrix than in the corresponding pure complex powders, which can be attributed to the restriction of molecular motion of complexes by the polymer chain networks and the exclusion of water molecules from the complex. We also found that the luminescence intensity decreased with increasing content of alpha-methylacrylic acid in the copolymer system. The lifetime of the lanthanide complexes also lengthened when they were incorporated in the polymer matrix. In addition, we found that the relationships between emission intensity and Tb (Eu) content exhibit some extent of concentration quenching.

Progress in the chemistry of spirodilactone and its derivations

Spirodilactones are a series of compounds with the structures of spiro-carbon and lactone which result in the special physical and chemical characters of Spirodilactones, In this paper the advance in the methods of synthesis, derivative reaction, chrial resolution, polymer synthesis of the most representative aspects for spirodi-gamma -butylactone and its derivations , were summarized described.

STUDY ON STRUCTURE-ACTIVITY-RELATIONSHIPS OF ORGANIC-COMPOUNDS - 3 NEW TOPOLOGICAL INDEXES AND THEIR APPLICATIONS

In this paper, three new topological indices, A(x1), A(x2), and A(x3), have been developed for use in multivariate analysis in structure-property relationship (SPR) and structure-activity relationship (SAR) studies. Good results have been obtained by using them to predict the physical and chemical properties and biological activities of some organic compounds.

Mineral chemistry and its genetic significance of olivine in Cenozoic basalts from the South China Sea

We dredged lots of Cenozoic basalts from areas covered from the northern sub-slope to the southern sub- slope of the South China Sea. Based on the study on mineral chemistry of clinopyroxenes in these Cenozoic hasalts, this paper indicates that pyroxenes are mostly enstatite and a few of augite, sahlite and Ca-rich pyroxene. Pyroxene microlite has higher content in, Ca, Ti and Fe than pyroxene phenocryst, it may reflect that the evolution trend of host magma of pyroxene is coincidence with that of alkali rock series. The depth of magma chambers which calculated from equilibrium temperatures and pressures between clinopyroxene and melt are as follows, that of magma of tephrite is about 49km, that of magma of trachybasalt is about 25km, and that of magma of basalt is about 15km. Correspondingly, Equilibrium temperatures( K) of three types rocks mentioned above gradually decrease from 1535 1498 to 1429 to 1369. By using discriminant plot which developed from pyroxene and alkali discriminant diagram of host rock, Cenozoic basalt from the South China Sea belongs to intraplate alkali basalt. The results suggest that alkali basalt series in the study area may be the products of continuous evolution of mantle plume, which result from some physical and chemistry process including partial melting and fractional crystallization of mantle plume during the course of its ascent to the surface.

Distribution pattern of marine flagellate and its controlling factors in the central and north part of the Huanghai Sea in early summer

A survey was carried out in the central and north part of the Huanghai Sea (34.5degrees similar to 37.0degreesN, 120.5degrees similar to124.0degreesE) during June 12 similar to 27, 2000. It was found that the abundance of marine flagellate ranged from 45 to 1278 cell/ml, 479 cell/ml in average. Flagellate was more abundant in the central part than in the north part of Huanghai Sea, and the abundance decreased with the increasing distance from the coast, showing a similar distribution pattern with isotherm. Vertically, high density of flagellate was always presented in the bottom of thermocline, and formed a dense accumulation in the central area of the Huanghai Sea Cold Water Mass. The effects of physical and biological factors on the distribution of marine flagellate in early summer were discussed. Water temperature (especially the existence of thermocline) rather than salinity showed significant effect on the distribution pattern of marine flagellate in the Huanghai Sea in early summer. When comparing the abundance of marine flagellate with that of other microorganisms, it revealed a comparatively stable relationship among these organhisms, with a ratio of heterotrophic bacteria: cyanobacteria: flagellate: dinoflagellate: ciliate being 10(5) 10(3):10(2):10(1):10(0).

A three-dimensional coupled physical-biological model study in the spring of 1993 in the Bohai Sea of China

A three-dimensional (3-D) coupled physical and biological model was used to investigate the physical processes and their influence on the ecosystem dynamics of the Bohai Sea of China. The physical processes include M-2 tide, time - varying wind forcing and river discharge. Wind records from I to 31 May in 1993 were selected to force the model. The biological model is based on a simple, nitrate and phosphate limited, lower trophic food web system. The simulated results showed that variation of residual currents forced by M, tide, river discharge and time-varying wind had great impact on the distribution of phytoplankton biomass in the Laizhou Bay. High phytoplankton biomass appeared in the upwelling region. Numerical experiments based on the barotropic model and baroclinic model with no wind and water discharge were also conducted. Differences in the results by the baroclinic model and the barotropic model were significant: more patches appeared in the baroclinic model comparing with the barotropic model. And in the baroclinic model, the subsurface maximum phytoplankton biomass patches formed in the stratified water.