Hydrate-based carbon dioxide capture from simulated integrated gasification combined cycle gas

The equilibrium hydrate formation conditions for CO2/H2 gas mixtures with different CO2 concentrations in 0.29 mol% TBAB aqueous solution are firstly measured.The results illustrate that the equilibrium hydrate formation pressure increases remarkably with the decrease of CO2 concentration in the gas mixture.Based on the phase equilibrium data,a three stages hydrate CO2 separation from integrated gasification combined cycle (IGCC) synthesis gas is investigated.Because the separation efficiency is quite low for the third hydrate separation,a hybrid CO2 separation process of two hydrate stages in conjunction with one chemical absorption process (absorption with MEA) is proposed and studied.The experimental results show H2 concentration in the final residual gas released from the three stages hydrate CO2 separation process was approximately 95.0 mol% while that released from the hybrid CO2 separation process was approximately 99.4 mol%.Thus,the hybrid process is possible to be a promising technology for the industrial application in the future.     

用于合成纯硅分子筛 AST 和 LTA 的动态有机结构导向剂(英文)

Pure-silica-zeolite(PSZ) AST and LTA are synthesized successfully by using the same structure-directing agent(SDA) molecule,but at different concentrations.A dynamic organic SDA is proposed to discuss the mechanism of phase discrimination between AST and LTA.Data suggest that the SDA molecules can self-assemble into dimer or trimer complexes at different concentrations by π-π interactions,and these differences can be taken advantage of to selectively synthesize either PSZ AST or LTA.These deviations from the Liebau's rules indicate that small changes in SDA chemistry,structure,and order in solution can have a great impact on the structure selectivity of the zeolite synthesis.     

A STUDY ON SNOW PROFILES AND SURFACE CHARACTERISTICS ALONG 6000km TRANSANTARCTIC ROUTE (Ⅰ)——THE "1990 INTERNATIONAL TRANS-ANTARCTIC EXPEDITION" GLACIOLOGICAL RESEARCH

Along a 5986 km route on Antarctic ice sheet from west to east, 106 snow pits with a depth ranging from 1.0—2.0 m have been dug by the first author of this paper, the Chinese member of the "1990 International Trans-Antarctic Expedition". The basic physical characteristics of the surface layer of the ice sheet on a large scale are obtained through the observations of snow profiles at these snow pits. The sastrugi shapes and major axis azimuths have also been observed or measured on the way. Analysis for these observation data shows that in West Antarctica the meltwater infiltration-congelation is obvious and the annual precipitation is larger than that in East Antarctica, which implies that climate in West Antarctica is warmer, more humid and influenced more greatly by the South Ocean than that in East Antarctica. Radiation ice-glazes frequently found in snow profiles indicate that even in East Antarctica under very low temperatures, surface "melting" occurs in summer due to the long-time solar radiatio     

A Theoretical Model of Energy Transfer between Rare Earth Ions in Crystals

The limitation of the random walk theory of energy transfer between rare earth ions in crystals published in literatures is pointed out in this paper. A modified model, which can be used in any level of rare earth ion concentration when the interaction between donor and acceptor is different from that between donors, is introduced. measured fluorescence lifetimes of Yb^3＋：YAl3（BO3）4 This model has been applied to analyze the with a series of Yb^3＋ concentrations.     

Error of DIAL-measured Ozone Concentration and a Three-Wavelength Inversion Technique

Sensitivity of the error in the stratospheric ozone concentration measured by DIAL to the scattering property of the stratospheric aerosol is studied through both theoretical analysis and numerical experiment in this paper, and based on the sensitivity, a three-wavelength lidar inversion technique is proposed for a simultaneous determination of ozone concentration profile, aerosol backscatter coefficient profile and its size distribution in the stratosphere. It is found from the sensitivity study that there is a considerable effect of the stratospheric aerosol on accuracy of the ozone concentration solution. If the aerosol scattering is neglected, a large error of the solution can be obtained, especially when there is the stratospheric volcanic cloud, the error can be up to 100%. According to numerical experiments, a great improvement of the ozone concentration solution is obtained by using the present three-wavelenght inversion method.     

Photopolymerization of Cyclohexene Oxide Initiated with Iron-arene Complex

Two iron-arene complex photoinitiators with different substituents in arene ligands were synthesized, their activities in initiating photopolymerization of cyclohexene oxide (CHO) were compared with that of IRGACURE 261, a commercialized photoinitiator from Ciba-Geigy. A higher activity was found when the arene ligand was substituted with a stronger electron donating group. For the system initiated by IRGACURE 261 the concentration of active centers in CHO polymerization was determined and it was found that the concentration is maximum at around 35℃. The post (dark) polymerization was significant, the polymerization yield decreased with the increase of irradiation temperature and increased with the increase of post polymerization temperature. The results are interpreted based on the mechanism proposed by Lohse, et al..     

A Study on Bilirubin Radical Cation Generated by One-Electron Oxidation

Introduction Bilirubin (BR) is generally regarded as a toxic compound when accumulated at an abnormally high concentration in biological tissues, and in fact a normal adult man produces about 300 mg of BR a day. However, it was proposed that the bile pigments BR and biliverdin(BV), which is the precursor of BR, may protect vitamin A and linoleie acid from oxidative destruction in the intestinal tract Further stud     

Solubility of stearic acid in supercritical CO_2-acetonitrile mixtures

The solubility of stearic acid in supercritical CO2 with acetonitrile (CH3CN) cosolvent was measured at 318.15 K in the pressure range from 9.5 to 16.5 MPa, and the cosolvent concentration ranges from 0. 0 to 5.5 mol% . The solubility increases with acetonitrile concentration and pressure, and it also increases with the apparent density of CO2 d1(moles of CO2 in per liter of fluid) at higher cosolvent concentrations. At lower d1, however, the solubility of the acid at lower acetonitrile concentrations is lower than that in pure CO2 provided that d1 is fixed, which is discussed qualitatively based on the clustering of the components in the system.     

The Origin of Alligator sinensis

Alligator sinensis and Alligator mississippiensis are put under the Alligator family and Alligator genus as two different species and have been thought that they are closely related in taxonomy. The results of our DNA-DNA hybridization experiments showed that A. sinensis is a relatively young species originated in Asia,whereas A. mississippiensis is the older.It seems that the alligator and crocodilian could evolve from each other.The evolutionary rate of the crocodilian is slower than those of birds and higher vertebrates.The phylogeny of four crocodilians have been obtained and the hypothesis that the ancestor of Crocodylus porosus is a transitional form between A.mississippiensis and A.sinensis is proposed.     

CATALYTIC ACTIVITY OF Pd-Sn COMPLEX CARBONYLATION OF ACETYLENE

The influence of different concentration of HO, SnCl2, Cl- and n-BuOH on the carbonylation of acetylene has been studied. The results show that the yield of n- butyl propionate increases with the increase of HC1 concentration and the catalytic activity is depressed when Cl" concentration increases. However, the stability of catalytic complex is promoted by Cl-. The key to the carbonylation of acetylene lies in the addition of SnCl2, which promotes the formation of the complex of C2H2, CO with catalyst and plays an important role in the hydrogen removal from n-BuOH. The hydrogen removed from n BuOH is the hydrogen source of this reaction. Meanwhile, the principle of the effect of HCl, Cl- and SnCl2 on reaction has been discussed. The reaction model has also been proposed.     

Open-pore biodegradable foams prepared via gas foaming and microparticulate templating

Open-pore biodegradable foams with controlled porous architectures were prepared by combining gas foaming and microparticulate templating. Microparticulate composites of poly(epsilon-caprolactone) (PCL) and micrometric sodium chloride particles (NaCl), in concentrations ranging from 70/30 to 20/80 wt.-% of PCL/NaCl were melt-mixed and gas-foamed using carbon dioxide as physical blowing agent. The effects of microparticle concentration, foaming temperature, and pressure drop rate on foam microstructure were surveyed and related to the viscoelastic properties of the polymer/microparticle composite melt. Results showed that foams with open-pore networks can be obtained and that porosity, pore size, and interconnectivity may be finely modulated by optimizing the processing parameters. Furthermore, the ability to obtain a spatial gradient of porosity embossed within the three-dimensional polymer structure was exploited by using a heterogeneous microparticle filling. Results indicated that by foaming composites with microparticle concentration gradients, it was also possible to control the porosity and pore-size spatial distribution of the open-pore PCL foams.     

Antarctic marine sediments as fingerprints of pollution migration

Forty elements in 21 coastal marine sediment samples collected duringthe second Antarctic scientific expedition from 18 different sites of Brekilenarea located at the coast of Antarctica were analysed by instrumental neutronactivation analysis (INAA) to detect eventual pollution. Radio-assay schemesfor three sets of elements after neutron irradiation and cooling were evolvedto avoid matrix effects. Data have been compared with those for sedimentsof various stations at Antarctica and two other regions in different continents.Lower concentration of certain elements in the Antarctic sediments reflectsless environmental exposition. Enrichment factors (EF) were calculated forall the elements using the earth crust as reference matrix, based on elementalvalues by MASON, TAYLOR and WEDEPOHL which show a normal pattern near to unityexcept for Ag and Br. The data obtained could also serve as a reference pointfrom which changes in the global environment can be studied. The quality assuranceof data was performed using standard reference materials (SRMs) of a similarmatrix (IAEA Marine Sediment SD-M/TM and Chinese Marine Sediment GBW 07313).     

Interaction forces between colloidal particles in a solution of like-charged, adsorbing nanoparticles

We have measured the force between a weakly charged micron-sized colloidal particle and flat substrate in the presence of highly charged nanoparticles of the same sign under solution conditions such that the nanoparticles physically adsorb to the colloidal particle and substrate. The objective was to investigate the net effect on the force profile between the microparticle and flat substrate arising from both nanoparticle adsorption and nanoparticles in solution. The experiments used colloidal probe atomic force microscopy (CP-AFM) to measure the force profile between a relatively large (5 μm) colloidal probe glass particle and a planar glass substrate in aqueous solutions at varying concentrations of spherical nanoparticles. At very low nanoparticle concentrations, the primary effect was an increase in the electrostatic repulsion between the surfaces due to adsorption of the more highly charged nanoparticles. As the nanoparticle concentration is increased, a depletion attraction formed, followed by longer-range structural forces at the highest nanoparticle concentrations studied. These results suggest that, depending on their concentration, such nanoparticles can either stabilize a dispersion of weakly-charged colloidal particles or induce flocculation. This behavior is qualitatively different from that in nonadsorbing systems, where the initial effect is the development of an attractive depletion force.     

Mass transfer of water-insoluble organic compound from octadecylsilyl-silica gel into water in the presence of a nonionic surfactant

The release of perylene from octadecylsilyl (ODS)-silica gel into water using a nonionic surfactant was kinetically studied by single microparticle injection and absorption microspectroscopy techniques. The release of perylene from the porous microparticles significantly depended on the surfactant concentration. The release rate constant was inversely proportional to the microparticle radius; the rate-determining step was the process at the spherical microparticle surface. The mechanism is discussed in terms of the solubilization of perylene at the microparticle surface by the micelle.     

Bioaccumulation of vanadium in the epiphytic lichen Parmelia caperata from Liguria (north-west Italy)

The concentration of vanadium was measured in 35 samples of the epiphytic lichen Parmelia caperata collected along the coast of the Ligurian Sea (Italy), in order to detect the possible bioaccumulation of vanadium due to a huge crude oil burning occurred in that area in 1991. The cartographic elaboration of data shows a pattern of distribution of vanadium concentrations according to different degrees of deviation from background condition, showing that 8 years later memory of the accident is still detectable in foliose lichen thalli.     

Determination of total metals in cultivated oysters (Crassostrea gigas) from the northwest coast of Mexico by microwave digestion and atomic absorption spectrometry.

Bivalves such as oysters often accumulate heavy metals, and therefore can be used to monitor changes of pollutant concentrations in the environment. Cultivated oysters from the northwest coast of Mexico are widely used for human consumption and thus have an important commercial value. Information was gathered on the concentration of these elements in oysters (Crassostrea gigas) cultivated on the coast of Sonora. Oysters were randomly collected from April to October 1997, from 6 different locations (65 individuals per site) in 4 different months. Metals were determined by microwave digestion followed by atomic absorption spectroscopy. The mean values (microg/g fresh weight) for each metal were: Cd, 0.76; Cu, 3.64; Zn, 17.71; Pb, 0.50; As, 0.05; Hg, 0.03; and Se, 0.21. The results show that, except for Cd, concentrations of regulated metals were under the maximum permitted values specified by regulatory agencies of Mexico and were comparable to those reported from other areas.     

Industrial contaminants in Antarctic biota

A critical review of the levels and patterns of industrial contaminants in biota from Antarctica and the Southern Ocean revealed that concentrations are low with respect to other regions of the world, although in some specimens/species (e.g. leopard seal, some invertebrates) they are occasionally high and comparable to those found in regions with a strong human impact; the highest levels of persistent organic pollutants (POPs) were detected in the vicinity of scientific stations. Bioconcentration prevails at the lower trophic levels of pelagic food webs, while biomagnification can become the main route of contamination at higher levels. In a benthic food web, biomagnification poses a major risk for organisms that accumulate lipids to overwinter, compared to those that accumulate glycogen. Hexachlorobenzene, DDTs and chlordanes showed similar concentrations and patterns in the 1980s-1990s period in organisms from Western and Eastern Antarctica, while the polychlorinated biphenyls time trend was different in a variety of species from the two regions.     

Distribution of 210Pb and 137Cs in Snow and Soil Samples from Antarctica

Abstract

This paper reports some results on natural and artificial radionuclide distribution in snow samples collected at the Priestly Nevé—Plateau (inland, 1998 m a.s.l.) and the Vegetation Island (near the coast, 200 m a.s.l.) stations, and in a soil sample from Wood Bay station, both near the Italian Base at Terranova Bay in Antarctica. Data on Pb-210 and Cs-137 in snow samples from an 80 cm deep trench and in granulometric fractions of a soil core are discussed.     

Determination of uranium, thorium and rare-earth elements in zircon samples using ICP-MS

Zircon is an accessory mineral, which occurs at low concentrations in a wide variety of rocks and is a host for hafnium, rare-earth elements (REE) and radio active elements like uranium and thorium. The presence of uranium in zircon has led to its increased use in the age determination of rocks. Zirconium is also considered as a strategic, hi-tech element because of its various applications, especially in the manufacturing, nuclear and aerospace industries. Analysis of zircon constitutes one of the tough tasks in analytical chemistry as it is a highly resistant mineral and it is extremely difficult to achieve its complete decomposition. In the present work, inductively coupled plasma mass spectrometry has been applied to the determination of hafnium, REE, uranium and thorium in zircon samples using two different sample dissolution procedures, one employing sodium peroxide fusion and another using a fusion mixture of KHF₂ and NaF in 3:1 ratio. Some selected zircon samples originating from different places on the eastern coast of India have been analysed by both the methods and values obtained by both methods were found to be in good agreement with each other. Though a number of international zircon reference materials are available, certified or even proposed values are available only for a very few elements in them. Two zircon reference materials have also been analysed by both methods and usable values have been proposed in this paper. The values obtained by both methods were found to compare well with each other and as well with those reported in literature. The % RSD for all the estimated elements varied from 1.0 to 12.0% at different concentration levels.     

Dielectrophoretic cell trapping for improved surface plasmon resonance imaging sensing

The performance of conventional surface plasmon resonance (SPR) biosensors can be limited by the diffusion of the target analyte to the sensor surface. This work presents an SPR biosensor that incorporates an active mass‐transport mechanism based on dielectrophoresis and electroosmotic flow to enhance analyte transport to the sensor surface and reduce the time required for detection. Both these phenomena rely on the generation of AC electric fields that can be tailored by shaping the electrodes that also serve as the SPR sensing areas. Numerical simulations of electric field distribution and microparticle trajectories were performed to choose an optimal electrode design. The proposed design improves on previous work combining SPR with DEP by using face‐to‐face electrodes, rather than a planar interdigitated design. Two different top‐bottom electrode designs were experimentally tested to concentrate firstly latex beads and secondly biological cells onto the SPR sensing area. SPR measurements were then performed by varying the target concentrations. The electrohydrodynamic flow enabled efficient concentration of small objects (3 μm beads, yeasts) onto the SPR sensing area, which resulted in an order of magnitude increased SPR response. Negative dielectrophoresis was also used to concentrate HEK293 cells onto the metal electrodes surrounded by insulating areas, where the SPR response was improved by one order of magnitude.