Showing papers by "Ocean University of China published in 2002"

A general circulation model study of the dynamics of the upper ocean circulation of the South China Sea

Abstract: [1] The temporal-spatial structure and the formation mechanisms of the South China Sea (SCS) circulation are studied using the Princeton Ocean Model (POM). The model well reproduces the observed sea surface height (SSH) annual cycle and some current system such as the SCS Western Boundary Current (SCSWBC) system and the Kuroshio Loop Current (KLC). Four sensitivity experiments are carried out to reveal the dynamic mechanisms of the SCS circulation. The results show that most of the seasonal variability of the SCS is controlled predominantly by wind forcing. The Kuroshio affects the mean SSH significantly but contribute little to the variability. The SCSWBC system consists of the SCS Warm Current (SCSWC) and the Vietnam Coastal Current (VCC). In winter the SCSWBC splits into two branches separated at similar to14degrees-18degreesN. The northern branch is the SCSWC flowing northward and the southern branch is the VCC flowing southward. In summer, however, the SCSWBC flows unidirectionally northward from the Karimata Strait to the Taiwan Strait. The temporal variation of the SCSWBC, especially the VCC, is determined by the wind forcing over the interior SCS. Buoyancy forcing can strengthen (weaken) the summer (winter) SCSWBC. The KLC is crucial to the SCS circulation north of 18degreesN. It ultimately determines the appearance of the SCSWC in winter.

Molecular Affinity and Permeability of Different Molecular Weight Chitosan Membranes

Abstract: Membranes were prepared from chitosan with different molecular weights by a casting method. The molecular affinity and permeability of the membranes for sodium chloride, glucose, tyrosine, and bovine serum protein were measured at 4 °C and pH 7. The molecular permeability of the chitosan membranes was inversely related to molecular weight. All prepared membranes showed a molecular affinity to bovine serum protein. The higher the molecular weight of chitosan membrane, the higher the affinity and the lower permeability of the membrane to bovine serum protein. Keywords: Chitosan; membrane; molecular permeability; molecular affinity; bovine serum protein

Observation of hurricane-generated ocean swell refraction at the Gulf Stream north wall with the RADARSAT-1 synthetic aperture radar

Abstract: We analyze the refraction of long oceanic waves at the Gulf Stream's north wall off the Florida coast as observed in imagery obtained from the RADARSAT-1 synthetic aperture radar (SAR) during the passage of Hurricane Bonnie on August 25, 1998. The wave spectra are derived from RADARSAT-1 SAR images from both inside and outside the Gulf Stream. From the image spectra, we can determine both the long wave's dominant wavelength and its propagation direction with 180/spl deg/ ambiguity. We find that the wavelength of hurricane-generated ocean waves can exceed 200 m. The calculated dominant wavelength from the SAR image spectra agree very well with in situ measurements made by National Oceanic and Atmospheric Administration National Data Buoy Center buoys. Since the waves mainly propagate toward the continental shelf from the open ocean, we can eliminate the wave propagation ambiguity. We also discuss the velocity-bunching mechanism. We find that in this very long wave case, the RADARSAT-1 SAR wave spectra should not be appreciably affected by the azimuth falloff, and we find that the ocean swell measurements can be considered reliable. We observe that the oceanic long waves change their propagation directions as they leave the Gulf Stream current. A wave-current interaction model is used to simulate the wave refraction at the Gulf Stream boundary. In addition, the wave shoaling effect is discussed. We find that wave refraction is the dominant mechanism at the Gulf Stream boundary for these very long ocean swells, while wave reflection is not a dominant factor. We extract 256-by-256 pixel full-resolution subimages from the SAR image on both sides of the Gulf Stream boundary, and then derive the wave spectra. The SAR-observed swell refraction angles at the Gulf Stream north wall agree reasonably well with those calculated by the wave-current interaction model.

Capture and Synthesis of 3D Surface Texture

Abstract: We present and compare five approaches for capturing, synthesising and relighting real 3D surface textures. Unlike 2D texture synthesis techniques they allow the captured textures to be relit using illumination conditions that differ from those of the original. We adapted a texture quilting method due to Efros and combined this with five different relighting representations, comprising: a set of three photometric images; surface gradient and albedo maps; polynomial texture maps; and two eigen based representations using 3 and 6 base images. We used twelve real textures to perform quantitative tests on the relighting methods in isolation. We developed a qualitative test for the assessment of the complete synthesis systems. Ten observers were asked to rank the images obtained from the five methods using five real textures. Statistical tests were applied to the rankings. The six-base-image eigen method produced the best quantitative relighting results and in particular was better able to cope with specular surfaces. However, in the qualitative tests there were no significant performance differences detected between it and the other two top performers. Our conclusion is therefore that the cheaper gradient and three-base-image eigen methods should be used in preference, especially where the surfaces are Lambertian or near Lambertian.

Spatial and temporal variability of trace metals in aerosol from the desert region of China and the Yellow Sea

Abstract: [i] From spring to early summer of 1995 and 1996, about 180-190 aerosol samples were collected from three observatories at Northwest China desert region (i.e., Minqin), coastal suburb area (i.e., Qingdao), and an island in the Yellow Sea (i.e., Qianliyan), respectively. The samples were analyzed to determine the concentrations of trace metals (Al, Fe, Mn, Na, Cr, Zn, Cu, Co, Ni, Pb, V, Sr, and Cd). Data are examined to understand the distribution of trace metals in aerosols at an upwind desert region and downwind marine recipient under westerly flow. The result shows that trace metal composition of aerosols vary considerably in time and space. Trace metal levels display a drastic seasonal change at both Qingdao and Qianliyan, with concentrations generally 2-3 times higher in spring than summer. Daily variation of trace metal concentrations at Minqin is more significant than Qingdao and Qianliyan, however. The enrichment factors for the crustal source (EF crust ) at Minqin are relatively low and unimportant compared with those at Qingdao and Qianliyan. Some of the trace species like Pb, Zn, and Cd have relatively high contributions from the anthropogenic source (Rp), and >98% are found at Qingdao and Qianliyan, with EF crust values 1-2 orders of magnitude higher than Minqin. Manganese is mainly from low-temperature weathering products and the contribution from crustal source (R c ) is >70% at Qingdao and Qianliyan. The coastal atmosphere responds to the episodic dust storms in the desert region (i.e., Minqin) by an increase in aerosol level and a higher concentration of crust-dominated materials. The percentage contributions from the crustal source (Rc) of trace metals, such as Pb, Cd, and Zn, could be increased considerably by 5 - 10 folds higher during the passage of cold fronts than during calm weather period over the Yellow Sea.

In vitro cytotoxicity of the organophosphorus insecticide methylparathion to FG-9307, the gill cell line of flounder (Paralichthys olivaceus).

Abstract: FG-9307, a cell line derived from the gill of flounder Paralichthys olivaceus, was used to determine the acute cytotoxic effects of the organophosphorus insecticide methylparathion. The cytotoxic effects of methylparathion were initially measured by three endpoint systems: neutral red (NR) uptake assay, tetrazolium (MTT) assay, and cell protein assay. Results indicated that concentrations of methylparathion ranging from 5 μg/ml to 60 μg/ml were toxic, and there was no significant difference in cytotoxic effects between the three test systems. Thus, the FG-9307 cell line is one of several choices for evaluating the acute toxicities of organophosphorus insecticides such as methylparathion. The ultrastructure of the cells was also studied. It was found that the ultrastructure of the cells was markedly altered by methylparathion, as evidenced by dilation of mitochondria, breakdown of rough endoplasmic reticulum, nuclear necrosis, and production of numerous lysosomes and lipid vacuoles. This appears to be the first report that a marine fish cell line can be used for acute in vitro cytotoxicity evaluation of methylparathion.

A dual‐frequency approach for retrieving sea surface wind speed from TOPEX altimetry

Abstract: More than a dozen of wind speed (U) algorithms have been proposed during the past 2 decades, as a result of a continuing effort to improve altimeter wind measurement. The progress in terms of accuracy, however, is seen to be rather slow. The reported root mean square (RMS) error of prevailing algorithms varies mostly between 1.6 and 2.0 m/s for the dominant wind regime. As far as the TOPEX altimeter is concerned, three measured quantities, namely, the radar cross sections from Ku and C band (sigma(Ku) and sigma(C)), as well as the significant wave height (H-s), have been used in previous algorithm developments, resulting in a variety of single-, dual-, and three-parameter model functions. On the basis of the finding of a banded dependency of the U-sigma(Ku) relationship on sigma(C) a new approach for retrieving altimeter wind speed, termed linear composite method (LCM), is proposed in this study. The LCM model function appears as a set of sigma(C)-dependent linear relations between U and sigma(Ku). A unique advantage of this approach is that it allows the algorithm to be tuned or expanded for a given range of wind speed without affecting the rest. Over 1.7 million coincident TOPEX/NASA scatterometer (NSCAT) and TOPEX/QuikSCAT data covering a period of 2.5 years are used to adjust the model. Validation against extensive buoy measurements indicates that the LCM algorithm is almost unbiased and has an overall RMS error of 1.56 m/s, which is 12% lower compared to the algorithm in operational use [Witter and Chelton, 1991]. In addition, a small (2.5-6%, depending on the reference data set) but significant improvement is found for the LCM when compared to the most recent dual- parameter algorithm [Gourrion et al., 2002].

Effects of harvest stage on the total lipid and fatty acid composition of four cylindrotheca strains

Abstract: Four strains ofCylindrotheca (B156, B164, B196, and B200) were harvested at three phases in the growth curve and their total lipid and fatty acid composition were determined. Total lipid reached highest values in the late stationary phase in B156 (24.0%), B164 (26.6%) and B200 (17.3%), in the exponential phase in B196 (15.5%). Saturated fatty acids increased with the development of the culture in B156 and B196, and reached their highest values in the late stationary phase in B156 (41.7%) and B196 (45.1%), in the early stationary phase in B164 (45.4%) and B200 (37.6%). Monounsaturated fatty acids increased with the development of the culture in B196 and B200, and reached their highest values in the late stationary phase in B196 (32.4%) and B200 (32.8%), in the early stationary phase in B164 (31.0%) and in the exponential phase in B156 (29.3%). Polynsaturated fatty acids decreased in the later phases of the culture in B164, B196 and B200, and peaked in the exponential phase in B164 (29.5%), B196 (42.9%) and B200 (37.3%), and in the early stationary phase in B156 (32.0%).

Life Cycles of Blocking Flows Associated with Synoptic-Scale Eddies: Observed Results and Numerical Experiments

Abstract: An observational study is presented to confirm that the life cycle of blocking associated with synoptic—scale eddies is a transfer process between dispersion and nondispersion. In addition, numerical experiments are conducted. It is found that the synoptic—scale eddies seem to play a dominant role in the amplification of blocking, while the topography effect appears to play a phase-locking role. At the same time, the synoptic eddies tend to split into two branches during the onset of blocking. This supports the observational results obtained.

Contribution of biological processes to self-purification of water with respect to petroleum hydrocarbon associated with No. 0 diesel in Changjiang Estuary and Jiaozhou Bay, China

Abstract: Mesocosms in 25-m3 ethylene vinyl acetate or 4-m3 polyethylene bags were performed at two sites in China: Changjiang Estuary in spring–summer 1998, and Jiaozhou Bay in autumn 1999 and spring–summer 2000. The experiments were designed to show the contributions of physical, physicochemical and biological processes to self-purification of water with respect to the water-soluble fraction (WSF) of petroleum hydrocarbon associated with No.0 diesel (PHAD). Over the experimental periods, the WSF-PHAD concentration in water declined significantly. A kinetic model for WAS-PHAD distribution in multiphase environments – in this case water (W), suspended sediment (SS), phytoplankton (PPT), zooplankton (ZPT) and atmosphere (ATM) – was developed to estimate the contributions of the various processes. In the model, the key processes responsible for self-purification include (1) physical transport by volatilization from W to ATM; (2) biological transformation through biodegradation; (3) biological transfer involving bioconcentration by PPT and ZPT; and (4) physicochemical transfer through sorption by SS. Model parameters were determined from the mesocosm experiments and parallel laboratory experiments, or taken from the literature. It indicated that volatilization plays an important role in short-term self-purification especially regarding alkanes with relatively low molecular weight, accounting for 82.9±2.5%. After the volatilization stops, bioconcentration by PPT contributes greatly to long-term self-purification especially regarding alkanes of higher molecular weight and polycyclic aromatic hydrocarbons (PHAs), accounting for 0.7 – 17.8% with an average of 7.8±7.3%. The bioconcentration is dominated by biomass of PPT as well as the WSF-PHAD concentration. However, the biodegradation process makes the greatest contribution to both the short- and long-term self-purification, affecting alkanes of both lower and higher molecular weight as well as PHAs. The results suggest that it is necessary to take into account the biological processes of biodegradation and bioconcentration in estimating the self-purification of water with respect to oil pollutants.

Quantum dynamics of methanol: Hamiltonian, representation and intensity considerations

Abstract: Employing a body-fixed axis system and Jacobi coordinates, a model for the vibration–torsion–rotation Hamiltonian of the CH 3 OH molecule with large-amplitude internal motions has been derived. This Hamiltonian is expressed in terms of Jacobi coordinates and is partitioned in the form H A + H B + H int , where H A and H B are the rovibrational Hamiltonians of methyl group CH 3 and asymmetric rotor OH, and H int represents their interactions. The resulting Hamiltonian is used to carry out a pure quantum mechanical calculation for this kind of molecule or to construct the potential surface using observed data. The detailed discussion of the Hamiltonian is presented for the model with a rigid methyl group and a rigid OH, which describes five lower frequency vibrational modes and pure rotation in the molecule. We discuss the advantages of body-fixed Jacobi form of the Hamiltonian and solution strategies for practical programming. The properties of labels of the energy states, potential function and dipole moments are investigated according to the molecular symmetry group G 6 of methanol. Finally, the developed formulation is used to calculate the energy levels of CO-stretching–torsion–rotation for lower rotational excitation ( J ⩽5). Comparison of the calculated results with experimental ones is presented.

Aluminum in the Macrotidal Yalujiang Estuary: Partitioning of Al along the Estuarine Gradients and Flux

Abstract: Water samples were collected from the Yalujiang estuary in both flood periods (August 1992 and August 1994) and dry season (May 1996) and were analyzed for aluminum (Al). Al behaves non-conservatively in the Yalujiang estuary, and a significant loss (70–80%) in dissolved concentration is observed in the upper estuary, in spite of seasonal variation in water discharge and sediment load. About 0.4×106, tons of Al is annually transported from Yalujiang to the estuary, of which the particulate pool clearly dominates. The particulate Al flux through the Yalujiang contributes 35% of the total Al input from Chinese rivers to the Yellow Sea. The data sets from size fractionation and C-18 SPE separation demonstrate that a large fraction of dissolved Al is in colloidal (≈50%) and organically complex (≈60%) forms in the Yalujiang. The observed scavenging from solution to particulate pools in the estuary is most likely through the flocculation of colloidal and organic-complexed Al, which results in a considerable change in dissolved-particulate partitioning, shown by laboratory mixing experiments. Exchange between dissolved and particulate phases is examined by analysis of Kd, the distribution coefficient. The empirical relationship of Kd with chlorinity and suspended matter concentrations was investigated with field observations and model simulations. The model indicated that Kd values of Al are inversely related to the amount of total suspended matter, but Kd-chlorinity plots show different features between dry and flood seasons.

TOXICITY OF POLYCYCLIC AROMATIC HYDROCARBONS(PAHs) TO MARINE ALGAE

Abstract: The kinetic method was applied in testing the acute toxicity of four kinds of Polycyclic Aromatic Hydrocarbons (PAHs) to six species of marine algae, and a logistic regression model was used to calculate the value of EC_(50). It show that the values of EC_(50) obtained from the model were in good agreement with those from its definition and this model revealed the correct and reasonable trait when the subtoxic stimulus was present. The value of 72h-EC_(50) was 34.1-114 mg/L, for toluene, 3.9-7.3 mg/L for naphthalene, 1.69-3.03 mg/L for 2-methlynaphthalene, 0.6-1.92 mg/L for phenanthrene to the phytoplankton. The order of the toxicity of four kinds of PAHs to six species of algae was: Nitzschia closterium minutissima > Zoaxanthella microadriz tica > Pheodacylum tricormutum Bohlin > Skeletonema costatum Greville > Chlorella vulgaris > Platymonas subcordiformis (Wille) Hazen. In addition, the results showed that it has a log-log correlation between the values of EC_(50) of four kinds of PAHs and of their K_(ow).

Nutrients in sediment pore water in tidal flat area in Yalujiang Estuary

Abstract: The concentrations of NO3-, PO(4)3- and SiO(3)2- in sediment pore waters from tidal flat area in Yalujiang Estuary were determined. The concentration of NO3- in sediment pore waters was almost stable, the average NO3- was 3.0 mumol/L. The concentration of PO(4)3- and SiO(3)2- were 0.8-70.4 mumol/L and 111.6-1054.3 mumol/L, respectively. The depth distribution of PO(4)3- and SiO(3)2- increased with depth at first and then decreased further down. The content of S2- in sediment raise with depth. Under the depth of 13 cm, Eh decreased into minus. pH did not obviously change with depth. The diffusion of nutrients in tidal flat area in Yalujiang estuary was from pore water into overlying water.

Structural Representation of Organometallics and Coordination Compounds and a Recommended Representation by Use of Dashed Lines

Abstract: By using broken lines to represent coordination interactions in organometallic and other coordinated compounds, we can draw structures satisfying the valencies of the atoms present. These broken lines should be used to replace many false single covalent bonds now used to depict organometallic and coordinated compounds. Chemical drawing software should not recognize such broken lines as single covalent bonds and they should be ignored. An example of confusing and erroneous structural representation of organometallics and coordination compounds is discussed.

A model describing the time course and variability in toxicity of hydrophobic chemicals to aquatic organisms: Toxicity of chlorinated benzenes to marine algae

Abstract: The growth of Chlorella marine, Nannochloris oculate, Pyramimonaos sp., Platymonas subcordiformis and Phaeodactylum tricornutum exposed to chlorobenzene, 1,2-dichlorobenzene, 1,2,3,4-tetrachlorobenzene and pentachlorobenzene was tested. The Boltzman equation was used to describe organism growth. The time course for uptake of hydrophobic organic chemicals (HOCs) by aquatic organisms was expressed by incorporating growth and, if desired, the effect of metabolism into the HOC bioconcentration process. The probability of any given concentration of HOCs in the organisms causing a specified toxic endpoint was expressed with a modified Weibull distribution function. The combined bioconcentration and probability equations were tested with data for time course of incubation of algae exposed to chlorinated benzenes (CBs). A set of parameters, including the uptake rate constant k 1, the elimination rate constant k 2 and thereafter the bioconcentration factor on a dry weight basis, BCF D, the critical HOC concentration in the organism resulting in a specified toxic endpoint, C A * , and the spread factor, S, could be obtained by fitting only experimental data for percent growth inhibition(%)-time-CB exposure concentration. The average coefficients of variation within CBs were 15.2% for BCF D, 21.0% for k 1, 18.3% for k 2, 8.1% for C A * and 9.7% for S. The variability in toxicity (such as EC10, EC50, EC90) derived from the model equations agreed well with those experimentally observed.

Enzymatic Synthesis of Methyl-Galactoaldehyde

Abstract: Methyl-galactosides were oxidized at room temperature by galactose oxidase in a one-step reaction and afforded methyl-galactoaldehyde in excellent yield and high purity. The resulting galactoaldehyde as a useful intermediate can be directly used in glycopeptide synthesis.