Investigation of Chemical Bond Characteristics, Thermal Expansion Coefficients and Bulk Moduli of alpha-R2MoO6 and R2Mo2O7 (R = rare earths) by Using a Dielectric Chemical Bond Method

Theoretical researches are performed on the alpha-R2MoO6 (R = Y, Gd, Tb Dy, Ho, Er, Tm and Yb) and pyrochlore-type R2Mo2O7 (R = Y, Nd, Sm, Gd, Tb and Dy) rare earth molybdates by using chemical bond theory of dielectric description. The chemical bonding characteristics and their relationship with thermal expansion property and compressibility are explored. The calculated values of linear thermal expansion coefficient (LTEC) and bulk modulus agree well with the available experimental values. The calculations reveal that the LTECs and the bulk moduli do have linear relationship with the ionic radii of the lanthanides: the LTEC decreases from 6.80 to 6.62 10(-6)/K and the bulk modulus increases from 141 to 154 GPa when R goes in the order Gd, Tb Dy, Ho, Er, Tm, and Yb in the alpha-R2MoO6 series; while in the R2Mo2O7 series, the LTEC ranges from 6.80 to 6.61 10(-6)/K and the bulk modulus ranges from 147 to 163 GPa when R varies in the order Nd, Sm, Gd, Tb and Dy.

Chemical bond characteristics, thermal expansion property and compressibility of AR(2)O(4) (A = Ca, Sr, Ba; R = rare earths)

Theoretical researches were performed on the CaFe2O4-type binary rare earth oxides AR(2)O(4) (A = Ca, Sr, Ba; R = rare earths) by using chemical bond theory of dielectric description. The chemical bond properties of these crystals were explored, and then the thermal expansion property and compressibility were studied. The theoretical values of linear thermal expansion coefficient (LTEC) and bulk modulus were presented. The calculations revealed that the LTECs and the bulk moduli do have linear relationship with the ionic radii of the rare earths. In the cases of Sc and Y, both the LTEC and bulk modulus values are larger than the lanthanide series. We attribute this to the difference in the electronic configuration between Sc (Y) and lanthanide series. For SrY2O4 and BaY2O4 crystals, the theoretical values of LTEC and bulk modulus agree well with experimental ones.

Effect of buffer capacity on electrochemical behavior of dopamine and ascorbic acid

It is well known that the electrochemical oxidation of dopamine and ascorbic acid includes the proton and electron transfers at a glassy carbon electrode and their redox potentials are dependent on the pH of solution. When the concentration of the buffer is not enough to neutralize the protons produced by electrochemical oxidation of dopamine and ascorbic acid, two peaks of them can be observed in cyclic voltammograms. The height of the new peak is in proportion to the concentration of proton acceptor including HPO42-, 2,4,6-trimethylpyridine, tris (hydroxymethyl) aminomethane. Moreover, the potential of it is dependent on the type and the concentration of buffer at the same pH of bulk solution. However, this phenomenon cannot be attributed to the interaction between proton acceptor and dopamine or ascorbic acid. So, we think the phenomenon is caused by the acute change of pH at the surface of working electrode. Similar results were also observed in the rotating disk voltammograms. It can be concluded that the electrochemical behavior of some compounds is dependent on the concentration of buffer when this concentration is not enough to neutralize the protons produced in electrochemical oxidation.

On improving the phase stability and thermal expansion coefficients of lanthanum cerium oxide solid solutions

The phase stability of lanthanum cerium oxide (La2Ce2O7), which is stable up to 1400 degrees C, and the thermal expansion coefficient of La2Ce2O7 doped with Ta2O5 or WO3 were studied. The thermal expansion coefficient of La2Ce2O7 below 400 degrees C was increased by adding more CeO2 or doping with either Ta2O5 or WO3.

Estimation thermal expansion coefficient from lattice energy for inorganic crystals

By using the study of the lattice energy and the structural parameters of binary inorganic crystals, a new parameter reflecting the thermal expansion property has been found, the relation between the linear expansion coefficient and new parameter has been established. A semiempirical method for evaluation of linear expansion coefficient from the lattice energy is presented, and developed to the complex crystals. The estimated values of the linear expansion coefficients of both simple and complex crystals are in good agreement with the experimental values.

Calculation of the thermal expansion coefficient for Bi2Sr2CaCu2O8

An estimation method of thermal expansion coefficient in term of lattice energy which was developed earlier for simple materials is extended to a complex material of Bi2Sr2CaCu2O8 (Bi-2212). The calculation of the chemical bond property and thermal expansion coefficient of Bi-2212 has been carried out and the theoretical values were in good agreement with the corresponding experimental results. The dependence of the thermal expansion coefficient on the different structures and on the flexible oxidation states of Bi and Cu are investigated. The results indicate that the thermal expansion coefficients of Bi-2212 are insensitive to the low lattice distortion of the average structure and the changes of formal valences of Bi and Cu ions.

Irreversible capacity loss of graphite electrode in lithium-ion batteries

The irreversible capacity loss of the carbon electrode in lithium-ion batteries at the first cycle is caused mostly by surface film growth. We inspected an unknown irreversible capacity loss (UICL) of the natural graphite electrodes. The charge/discharge behavior of graphite and meso-phase carbon microbeads heat-treated at 2800 degrees C (MCMB28) as the materials of the carbon anode in the lithium-ion battery were compared. It was found that the capacity loss of the natural graphite electrode in the first cycle is caused not only by surface film growth, but also by irreversible lithium-ion intercalation on the new formed surface at the potential range of lithium intercalation, while the capacity loss of the MCMB28 electrode is mainly originated from surface film growth. The reason for the difference of their irreversible capacity losses of these two kinds of carbon material was explained in relation to their structural characteristics. (C) 1997 Published by Elsevier Science S.A.

Antioxidant capacity and lipophilic content of seaweeds collected from the Qingdao coastline

Lipophilic extracts from 16 species of seaweeds collected along the Qingdao coastline were screened and evaluated for their antioxidant activities (AA) using the beta-carotene-linoleate assay system. The diethyl ether soluble extracts of all selected seaweeds exhibited various degrees of antioxidative efficacy in each screen. The highest antioxidant capacities among the tested samples were observed for Rhodomela confervoides and Symphyocladia latiuscula and were comparable with that of the well-known antioxidant butylated hydroxytoluene and greater than that of propyl gallate. The lipophilic content of all 16 samples and the chemical composition of 4 selected seaweeds, R. confervoides and S. latiuscula, which had higher AA, Laminaria japonica, which had intermediate AA, and Plocamium telfairiae, which had lower AA, were analyzed by gas chromatography and gas chromatography-mass spectrometry, respectively. Fatty acids and alkanes were found. The present data indicated an increase in antioxidative property with increasing content of unsaturated fatty acid. The result of this study suggests that seaweeds can be considered as a potential source for the extraction of lipophilic antioxidants, which might be used as dietary supplements or in production in the food industry. This is the first report on the antioxidant activities of lipophilic extracts from seaweeds.

Evaluation of 28 marine algae from the Qingdao coast for antioxidative capacity and determination of antioxidant efficiency and total phenolic content of fractions and subfractions derived from Symphyocladia latiuscula (Rhodomelaceae)

The extracts obtained from 28 species of marine algae were evaluated for their antioxidant activity (AA) versus the positive controls butylated hydroxytoluene (BHT), gallic acid (GA), and ascorbic acid (AscA). Most of the tested samples displayed antioxidant activity to various degrees. Among them, the extract of Symphyocladia latiuscula exhibited the strongest AA, which was comparable to BHT, GA, and AscA in radical scavenging activity, as shown in the DPPH (alpha,alpha-diphenyl-beta-picrylhydrazyl) assay, and higher than those of the positive controls in beta-carotene-linoleate assay system. In addition, the ethyl acetate-soluble fraction isolated from the crude extract of S. latiuscula exhibited the highest antioxidant activity in both assay systems. This fraction was further fractionated into seven subfractions (F1-F7) by vacuum liquid chromatography (VLC). F1 and F4 were found to be the most effective subfractions in scavenging DPPH radical assay and in the beta-carotene-linoleate assay, respectively. The total phenolic content (TPC) and reducing power (RP) for all of the extracts, fractions, and subfractions (F1-F7) were also determined. The TPC of the 28 extracts ranged from 0.10 to 8.00 gallic acid equivalents (mg/g seaweed dry weight) while the RP ranged from 0.07 to 11.60 ascorbic acid equivalents (mg center dot g(-1) seaweed dry weight). Highly positive relationships between AA and TPC as well as between AA and RP were found for the extracts and fractions, while for the subfractions F1-F7 only weak or no such relations were found. The results obtained from this study indicate that further analysis is needed of those marine algal species that contain the most antioxidant activity in order to identify the active principles.

Growth characters and photosynthetic capacity of Gracilaria lemaneiformis as a biofilter in a shellfish farming area in Sanggou Bay, China

Experiments on growth characters and ecological functions of the macroalgae Gracilaria lemaneiformis, collected from south China, were conducted in polyculture areas of kelp and filter-feeding bivalve in Sanggou Bay in Weihai City, Shandong, in north China from May 2002 to May 2003. The results of 116 days cultivation showed that the average wet weight of alga increased 89 times from 0.1 to 8.9 kg rope(-1), with an average specific growth rate ( based on wet weight) of 3.95% per day. The most favorable water layer for its growth was 1.0 - 1.8 m below the surface in July and August, with an average specific growth rate of 8.2% per day in 30-day experiments. Photosynthetic activity changed seasonally, with an average of 7.3 mg O-2 g dw(-1) h(-1). The maximum rate (14.4 mg O-2 g dw(-1) h(-1)) was recorded in July, or 19.3 mg CO2 g dw(-1) h(-1), while the minimum (0.40 mg CO2 g dw(-1) h(-1)) was in April. This study indicated that the culture of G. lemaneiformis is an effective way to improve water quality where scallops are cultivated intensively.

Capacity of soil to protect organic carbon and biochemical characteristics of density fractions in Ziwulin Haplic Greyxems soil

Physical protection is one of the important ways to stabilize organic carbon in soils. In order to understand the role of soils as a carbon sink or source in global climatic change and carbon cycles and properly manage soils as a carbon sink, we ought to know how many organic carbon (OC) in a given soil could be protected. By a density fractionation approach and ultrasonic technique, each soil sample was divided into three fractions: free light fraction (free-LF), occluded fraction (occluded-LF) and heavy fraction (HF). The obtained fractions were analyzed for total OC content, carbohydrate content and recalcitrant OC content. The results showed: (i) In the whole soil profile, dominance of OC consistently decreased in the following order: HF, free-LF, occluded-LF. This suggested that OC in soils were mostly protected. From 0-10 to 60-80 cm horizons, the OC in free-LF decreased from 25.27% to 3.72%, while OC in HF they were increased from 72.57% to 95.39%. The OC in occluded-LF was between 2.16% and 0.89%. (ii) Organic carbon recalcitrance in free-LF was similar to that in HF, and was even higher than that in HF below the surface horizon. This suggested that free-LF was not always the most fresh and non-decomposed fraction. OM quality of HF was higher than that of free-LF in the surface 10 cm below, namely the protected OM had higher quality than free OM in these horizons.

环渤海花岗岩体地下油库建设的工程地质力学研究

As a kind of strategic resource，petroleum play an very important role in current social stability, economic development and state safety. Since 1993 China has turned from a net oil exporter into a net oil importer, the figure of imported oil increased from then on. In 2004 China's total energy consumption exceeded Japan’s, and ranked in the second place, just inferior to America. Today China is the world’s third-largest importing nation, accounting for 6% of world imports and 8% of world consumption. Comparing with other strategic petroleum reserve schemes, underground oil storage possess many advantages, such as security, economy, less pollution, save land, suited for strategic reserve and so on, so it is the most ideal form for strategic petroleum reserve. In the background of China Strategic Petroleum Reserve Program started just now, this paper choose Circum-Bo sea region as a study area, and do some system study on the underground oil storage caverns constructed in inter-large granite rock masses in Circum-Bo sea region. On the foundation of a great amount of information come from both home and abroad, firstly this paper analysed the principle, economy, cavern shape, profile dimension, and gain some cognizances and logos, as follows: ①Hard rock mass such as granite is the major rock, in which underground oil storage are constructed; ②Unlined underground oil storage caverns had been wide spread used as a sort of oil storage form abroad, there already exist a suit of skilled experience and technologies to prevent oil product from leaking; ③Compared with surface tanks, underground oil storage cavern possess predominance in economy clearly. In general, it will be more economical when the storage capacity exceed 50000m3. The quality of rock mass is the most important factor for underground storage cost, however such as hydrogeology, storage capacity, the number of storage galleries, the length, storage product, mechanical equipments, geographic location also influent the cost. In designed depth of the underground storage, the rock mass of Jinzhou mainly belong to class Ⅱ, but parts with dykes, clayization alteration, and dense joints are Ⅲ, Ⅳ; ④Now, there are few underground oil storages span more than 25m in both abroad and home. The examples of some ancient underground works and modern underground excavation with wide span surely give us many precious elicitations to construct more great unlined storage caverns, when the rock mass quality is good, cavern shape and construction method also are proper, it is quite possible to construct underground oil storage cavern with span more than 30m . The main axis orientation of Jinzhou underground oil storage cavern is NW direction, the cavern's elevation locate between -53msl and -76msl. The storage's total volume is about 3×106m3, composed of 8 parallel galleries with 950m length, the pillars between them are 45m, and every two of galleries form one unit, which can deposit 75×104m3 for each unit. The product will be stored are Saudi light and Saudi medium crude oil, the main cavern's section is 411.5m2, with 23m height and 19m width. According to the principle and technique of engineering geomechanics, this study supply a sort of system scientific thinking and method for sitting location of underground oil storage in granite region: ① On the foundation of the earth crust stability sub-zone appraise of Circum-Bo sea region, farther research concerning granite distribution, genesis, geological period and fault structure are conducted in stable areas, generally, this paper select Liaoxi, east shore of Liaotung peninsula and Jiaotung peninsula as target areas for underground oil storage regions, where Mesozoic granite is magnitude; ②After roundly comparison in facts of geologic structure, engineering geology, hydrogeology, topography, transportation and so on of three granite distributed areas, at last, selecting Jingzhou granite zone in Liaoxi out as an ideal construction area; ③ Detailed investigation is conducted in the southeast of Baimashi in Jingzhou development district, the final field. Ultrasonic Borehole Television, as a major way to collect original information of borehole rock mass were used, which is very effective to appraise the quality of deep rock mass; ④ According to the field data of tectonic stress, rock mass quality, the spatial distribution of fracture water, some optimum designs in cross section, axial direction and cavern span have been designed for the underground oil storage cavern layout in Jinzhou. To understand the characteristics of swelling alteration rock in Jinzhou granite mass, collected abundant swelling alteration rock engineering examples in granite, which study them in detail, concluded the swelling alteration rock distribute nearly everywhere in China, intruded medium-basic dykes alteration, along discontinuities and mineral hydrothermal alteration with genesis of granite are three main forms clayization alteration rock in granite rock mass. In Jinzhou field, from macro to micro studied the swelling rock which induced by mid-basic dyke intrusion, with weak swelling. In conclusion, this paper conclude the distribution rule and features of expansion alteration rock in filed, and advise some technical suggestions for excavation at swelling alteration rock part. The main features of this paper: ①In the process of site selection, investigation and design, a suit of technique and method of engineering geomechanics metasynthesis were formed, which is significative to guide the large scale underground oil storage cavern sitting location, investigation and design in granite rock mass; ②The detailed discussion on the engineering geology problems in granite mass, such as weathering crust, faults, dykes and clayization alteration rock, are useful for other projects in aspects of site selection, engineering geology evaluation and stability estimation; ③The summary and integration of the genesis, type, countermeasure relate to swelling alteration rock, also is likely to be used for other underground oil storage caverns constructed in swelling alteration granite. In conclusion, this study is meaningful for guiding the large scale underground oil storage for site selection, investigation and design in granite rock mass.

南海张裂大陆边缘数值模拟研究

The South China Sea (SCS) is one of the largest marginal seas in the western Pacific, which is located at the junction of Eurasian plate, Pacific plate and Indian-Australian plate. It was formed by continent breakup and sea-floor spreading in Cenozoic. The complicated interaction among the three major plates made tectonic movement complex and geological phenomena very rich in this area. The SCS is an ideal place to study the formation and evolution of rifted continental margin and sea-floor spreading since it is old enough to have experienced the major stages of the basin evolution but still young enough to have preserved its original nature. As the demand for energy grows day by day in our country, the deep water region of the northern continental margin in the SCS has become a focus of oil and gas exploration because of its huge hydrocarbon potential. Therefore, to study the rifted continental margin of the SCS not only can improve our understanding of the formation and evolution processes of rifted continental margin, but also can provide theoretical support for hydrocarbon exploration in rifted continental margin. This dissertation mainly includes five topics as follows: (1) Various classic lithosphere stretching models are reviewed, and the continuous non-uniform stretching model is modified to make it suitable for the case where the extension of lithopheric mantle exceeds that of the crust. Then simple/pure shear flexural cantilever model is applied to model the basement geometries of SO49-18 profile in the northern continental margin of the SCS. By fitting the basements obtained by using 2DMove software with modeling results, it is found that the reasonable effective elastic thickness is less than 5km in this region. According to this result, it is assumed that there is weak lower crust in the northern continental margin in the SCS. (2) We research on the methods for stretching factor estimation based on various lithosphere stretching models, and apply the method based on multiple finite rifting model to estimate the stretching factors of several wells and profiles in the northern continental margin of the SCS. (3) We improve one-dimension strain rate inversion method with conjugate gradient method, and apply it to invert the strain rate of several wells in the northern continental margin of the SCS. Two-dimension strain rate forward modeling is carried out, and the modeling results show that effective elastic thickness is a key parameter to control basin’s geometry. (4) We simulate divergent upwelling mantle flow model using finite difference method, and apply this newly developed model to examine the formation mechanism of the northwest and central sub-basin in the SCS. (5) We inverse plate thickness and basal temperature of oceanic lithosphere using sea-floor ages and bathymetries of the North Pacific and the North Atlantic based on varied-parameters plate model, in which the heat conductivity, heat capacity and coefficient of thermal expansion depend on temperature or depth. A new empirical formula is put forward based the inversed parameters, which depicts the relation among sea-floor age, bathymetry and heat flow. Then various similar empirical formulae, including the newly developed one, are applied to examine the sea-floor spread issue in the SCS based on the heat flow and bathymetry data of the abyssal sub-basin.