Validation of a method of estimating age, modelling growth, and describing the age composition of Coilia mystus from the Yangtze Estuary, China

A collection of 577 Coilia mystus was made during April 2006 and 2007 from China's Yangtze Estuary to estimate the age structure and growth patterns of the population. Examination of sectioned sagittal otoliths revealed a periodic straight/curved growth pattern. The straight zone was from April to November, and the curved zone from October to May, indicating annual periodicity. Annual periodicity was also verified by margin zone analysis. The shift from a curved-zone to the next straight-zone stanza was defined as an annulus. The fish from which the otoliths were taken were 0-5 years old. The von Bertalanffy growth function was fitted to standard length (LS)-at-age data as L-S = 215.16 (1 - e(-0.53(t+0.30))) (n = 577, r(2) = 0.81, p < 0.05). The mature females included five age classes, ages 1 and 2 accounting for 74.3% of the population. The mature males included fish aged 1 and 2, those at age 1 accounting for 86.4% of the population. Mean length was smaller, and annual growth less, for mature males than for females of comparable age. The study demonstrated that the Yangtze population of C. mystus consists of more age classes than previously thought and that the age structure of the population needs to be considered in management decisions.

Interaction of a premixed flame with a liquid fuel film on a wall

© 2004 The Combustion Institute. Published by Elsevier Inc. All rights reserved. In piston engines and in gas turbines, the injection of liquid fuel often leads to the formation of a liquid film on the combustor wall. If a flame reaches this zone, undesired phenomena such as coking may occur and diminish the lifetime of the engine. Moreover, the effect of such an interaction on maximum wall heat fluxes, flame quenching, and pollutant formation is largely unknown. This paper presents a numerical study of the interaction of a premixed flame with a cold wall covered with a film of liquid fuel. Simulations show that the presence of the film leads to a very rich zone at the wall in which the flame cannot propagate. As a result, the flame wall distance remains larger with liquid fuel than it is for a dry wall, and maximum heat fluxes are smaller. The nature of the interaction of flame wall interaction with a liquid fuel is also different from the classical flame/dry wall interaction: it is controlled mainly by chemical mechanisms and not by the thermal quenching effect observed for flames interacting with dry walls: the existence of a very rich zone created above the liquid film is the main mechanism controlling quenching.

Relationships between microcystins and environmental parameters in 30 subtropical shallow lakes along the Yangtze River, China

1. A survey of 30 subtropical shallow lakes in the middle and lower reaches of the Yangtze River area in China was conducted during July-September in 2003-2004 to study how environmental and biological variables were associated with the concentration of the cyanobacterial toxin microcystin (MC). 2. Mean MC concentration in seasonally river-connected lakes (SL) was nearly 33 times that in permanently river-connected lakes (RL), and more than six times that in city lakes (NC) and non-urban lakes (NE) which were not connected to the Yangtze River. The highest MC (8.574 mu g L-1) was detected in Dianshan Lake. 3. MC-RR and MC-LR were the primary toxin variants in our data. MC-RR, MC-YR and MC-LR were significantly correlated with Ch1 a, biomass of cyanobacteria, Microcystis and Anabaena, indicating that microcystins were mainly produced by Microcystis and Anabaena sp. in these lakes. 4. Nonlinear interval maxima regression indicated that the relationships of Secchi depth, total nitrogen (TN) : total phosphorus UP) and NH4+ with MC were characterised by negative exponential curves. The relationships between MC and TN, TP, NO3- + NO2- were fitted well with a unimodal curve. 5. Multivariate analyses by principal component and classifying analysis indicated that MC was mainly affected by Microcystis among the biological factors, and was closely related with temperature among physicochernical factors.

Root zone microbial populations, urease activities, and purification efficiency for a constructed wetland

In order to investigate the effects of microorganisms and their urease activities in macrophytic root zones on pollutant removal, four small-scale plots (SSPs) of vertical/reverse-vertical flow wetlands were set up to determine: a) the relationship between the abundance of microorganisms in the root zones and water purification efficiency; and b) the relationship between urease activities in the root zones and pollutant removal in a constructed wetland system. Total numbers of the microbial population (bacteria, fungi, and actinomyces) along with urease activities in the macrophytic root zones were determined. In addition, the relationships between microbial populations and urease activities as well as the wastewater purification efficiencies of total phosphorus (TP), total Kjeldahl nitrogen (TKN), biochemical oxygen demand in 5 days (BOD5), and chemical oxygen demand (COD) were also analyzed. The results showed that there was a highly significant positive correlation (r = 0.9772, P < 0.01) between the number of bacteria in the root zones and BOD5 removal efficiency and a significant negative correlation (r = -0.9092, P < 0.05) between the number of fungi and the removal efficiency of TKN. Meanwhile, there was a significant positive correlation (r = 0.8830, P < 0.05) between urease activities in the root zones and the removal efficiency of TKN. Thus, during wastewater treatment in a constructed wetland system, microorganism and urease activities in the root zones were very important factors.

The role of Sb in the molecular beam epitaxy growth of 1.30-1.55 mu m wavelength GaInNAs/GaAs quantum well with high indium content

Sb-assisted GaInNAs/GaAs quantum wells (QWs) with high (42.5%) indium content were investigated systematically. Transmission electron microscopy, reflection high-energy electron diffraction and photoluminescence (PL) measurements reveal that Sb acts as a surfactant to suppress three-dimensional growth. The improvement in the 1.55 mu m range is much more apparent than that in the 1.3 mu m range.. which can be attributed to the difference in N composition. The PL intensity and the full-width at half maximum of the 1.55 mu m single-QW were comparable with that of the 1.3 Am QWs. (c) 2006 Elsevier B.V. All rights reserved.

Analysis of the interfaces of [NiFe/Mo](30) and [Fe/Mo](30) multilayers

The interface states of [NiFe/Mo](30) and [Fe/Mo](30) multilayers have been investigated by x-ray small angle reflection and diffuse scattering. Significant interface roughness correlation was observed in both ultrathin [NiFe/Mo](30) and [Fe/Mo](30) multilayers. An uncorrelated roughness of about 27-3.1 Angstrom was revealed in the [NiPe/Mo](30) multilayers, which is explained as originating from a transition layer between the NiFe and the Mo layers. By the technique of diffuse scattering, it is clearly indicated that the interfacial roughness of NiFe/Mo is much smaller than that of Fe/Mo although the lattice mismatch is the same in both multilayers.

The methane hydrate formation and the resource estimate resulting from free gas migration in seeping seafloor hydrate stability zone

It is a typical multiphase flow process for hydrate formation in seeping seafloor sediments. Free gas can not only be present but also take part in formation of hydrate. The volume fraction of free gas in local pore of hydrate stable zone (HSZ) influences the formation of hydrate in seeping seafloor area, and methane flux determines the abundance and resource of hydrate-bearing reservoirs. In this paper, a multiphase flow model including water (dissolved methane and salt)-free gas hydrate has been established to describe this kind of flow-transfer-reaction process where there exists a large scale of free gas migration and transform in seafloor pore. In the order of three different scenarios, the conversions among permeability, capillary pressure, phase saturations and salinity along with the formation of hydrate have been deducted. Furthermore, the influence of four sorts of free gas saturations and three classes of methane fluxes on hydrate formation and the resource has also been analyzed and compared. Based on the rules drawn from the simulation, and combined information gotten from drills in field, the methane hydrate(MH) formation in Shenhu area of South China Sea has been forecasted. It has been speculated that there may breed a moderate methane flux below this seafloor HSZ. If the flux is about 0.5 kg m-2 a-1, then it will go on to evolve about 2700 ka until the hydrate saturation in pore will arrive its peak (about 75%). Approximately 1.47 109 m3 MH has been reckoned in this marine basin finally, is about 13 times over preliminary estimate.

Study on the hydrolysis/precipitation behavior of Keggin Al-13 and Al-30 polymers in polyaluminum solutions

The hydrolysis/precipitation behaviors of Al3+, Al-13 and Al-30 under conditions typical for flocculation in water treatment were investigated by studying the particulates' size development, charge characteristics, chemical species and speciation transformation of coagulant hydrolysis precipitates. The optimal pH conditions for hydrolysis precipitates formation for AlCl3, PAC(A113) and PAC(A130) were 6.5-7.5, 8.5-9.5, and 7.5-9.5, respectively. The precipitates' formation rate increased with the increase in dosage, and the relative rates were AlCl3 >> PAC(A130) > PACA113. The precipitates' size increased when the dosage increased from 50 mu M to 200 mu M, but it decreased when the dosage increased to 800 AM. The Zeta potential of coagulant hydrolysis precipitates decreased with the increase in pH for the three coagulants. The isoelectric points of the freshly formed precipitates for AlCl3, PAC(A113) and PAC(A130) were 7.3, 9.6 and 9.2, respectively. The Zeta potentials of AlCl3 hydrolysis precipitates were lower than those of PAC(A113) and PAC(A130) when pH > 5.0. The Zeta potential of PAC(A130) hydrolysis precipitates was higher than that of PACA113 at the acidic side, but lower at the alkaline side. The dosage had no obvious effect on the Zeta potential of hydrolysis precipitates under fixed pH conditions. The increase in Zeta potential with the increase in dosage under uncontrolled pH conditions was due to the pH depression caused by coagulant addition. Al-Ferron research indicated that the hydrolysis precipitates of AlCl3 were composed of amorphous AI(OH)3 precipitates, but those of PACA113 and PACA130 were composed of aggregates of Al-13 and Al-30, respectively. Al3+ was the most un-stable species in coagulants, and its hydrolysis was remarkably influenced by solution pH. Al-13 and Al-30 species were very stable, and solution pH and aging had little effect on the chemical species of their hydrolysis products. The research method involving coagulant hydrolysis precipitates based on Al-Ferron reaction kinetics was studied in detail. The Al species classification based on complex reaction kinetic of hydrolysis precipitates and Ferron reagent was different from that measured in a conventional coagulant assay using the Al--Ferron method. The chemical composition of Al-a, Al-b and Al-c depended on coagulant and solution pH. The Al-b measured in the current case was different from Keggin Al-13, and the high Alb content in the AlCl3 hydrolysis precipitates could not used as testimony that most of the Al3+ Was converted to highly charged Al-13 species during AlCl3 coagulation.

On the acid-base stability of Keggin Al-13 and Al-30 polymers in polyaluminum coagulants

The acid-base stabilities of Al-13 and Al-30 in polyaluminum coagulants during aging and after dosing into water were studied systematically using batch and flow-through acid-base titration experiments. The acid decomposition rates of both Al-13 and Al-30 increase rapidly with the decrease in solution pH. The acid decompositions of Al-13 and Al-30 with respect to H+ concentration are composed of two parallel first-order and second-order reactions, and the reaction orders are 1.169 and 1.005, respectively. The acid decomposition rates of Al-13 and Al-30 increase slightly when the temperature increases from 20 to ca. 35 A degrees C, but decrease when the temperature increases further. Al-30 is more stable than Al-13 in acidic solution, and the stability difference increases as the pH decreases. Al-30 is more possible to become the dominant species in polyaluminum coagulants than Al-13. The acid catalyzed decomposition and followed by recrystallization to form bayerite is one of the main processes that are responsible for the decrease of Al-13 and Al-30 in polyaluminum coagulants during storage. The deprotonation and polymerization of Al-13 and Al-30 depend on solution pH. The hydrolysis products are positively charged, and consist mainly of repeated Al-13 and Al-30 units rather than amorphous Al(OH)(3) precipitates. Al-30 is less stable than Al-13 upon alkaline hydrolysis. Al-13 is stable at pH < 5.9, while Al-30 lose one proton at the pH 4.6-5.75. Al-13 and Al-30 lose respective 5 and 10 protons and form [Al-13] (n) and [Al-30] (n) clusters within the pH region of 5.9-6.25 and 5.75-6.65, respectively. This indicates that Al-30 is easier to aggregate than Al-13 at the acidic side, but [Al-13] (n) is much easier to convert to Alsol-gel than [Al-30] (n) . Al-30 possesses better characteristics than Al-13 when used as coagulant because the hydrolysis products of Al-30 possess higher charges than that of Al-13, and [Al-30] (n) clusters exist within a wider pH range.

Experimental study on flow characters of CH3CCl2F hydrate slurry

The flow behaviors of CH3CCl2F hydrate slurry with volume concentration of 10-70% were studied in a new built flow loop with a diameter of 42.0 mm and length of 30.0 m. Morphologies of the fluids from slurrylike hydrates to slushlike hydrates with increasing of hydrate volume concentration in pipeline were observed. Pressure drops in pipeline also were studied and an exceptional pressure transition zone with hydrate volume concentration between 30% and 40% was found for the first time, which can be used as a notation to judge if the pipeline runs safely or not. Fanning friction factors of the hydrate slurries with all hydrate contents tend to constants between 0.38 and 0.5, which depend on the volume concentration in slurries, when the velocity reaches 1.5 m/s. A simple relation to estimate the pressure drop of hydrate slurry in pipeline was presented and verified. Experimental results were compared to the estimated results, which showed a good agreement. 

30.4nm极紫成像探测器实验研究

中国科学院知识创新方向性项目(061Z291213) 资助课题