Laboratory Study on Sediment Diffusion and Deposition into Blind Channels

Any waterway with one end closed and the other open is generally called a blind channel. The main flow tends to expand, separate, and cause circulation at the mouth of blind channels. The main flow continuously transfers momentum and sediment into the circulation region through the turbulent mixing region (TMR) between them, thus leading to a large amount of sediment deposition in the blind channels. This paper experimentally investigated the properties of the water flow and sediment diffusion in TMR, demonstrating that both water flow and sediment motion in TMR approximately coincide with a similar structure as in the free mixing layer induced by a jet. The similarity functions of flow velocity and sediment concentration are then assumed, based on observation, and the resulting calculation of these functions is substantially facilitated. For the kind of low velocity flow system of blind channels with a finite width, a simple formula for the sediment deposition rate in blind channels is established by analyzing the gradient of crosswise velocity and sediment concentration in TMR.

Laboratory study on cracks in saturated sands

It has been reported([1]) that when a loosely packed column of saturated sand in a vertical cylindrical container is shock loaded axially by dropping to the floor, large horizontal cracks initiate, grow and eventually fade away in the sand as it settles under gravity. This paper shows that a similar phenomenon can also be observed when shock loading is replaced by forcing water to percolate upward through the sand column. It is believed that our result sheds further light on the physics of formation of these cracks.

A laboratory study on risk assessment of microcystin-RR in cropland

The persistence time and risk of microcystin-RR (MC-RR) in cropland via irrigation were investigated under laboratory conditions. In order to evaluate the efficiency of the potential adsorption and biodegradation of MC-RR in cropland and the persistence time of MC-RR for crop irrigation, high performance liquid chromatography (HPLC) was used to quantify the amount of MC-RR in solutions. Our study indicated that MC-RR could be adsorbed and biodegraded in cropland soils. MC-RR at 6.5 mg/L could be completely degraded within 6 days with a lag phase of 1 - 2 days. In the presence of humic acid, the same amount of MC-RR could be degraded within 4 days without a lag phase. Accordingly, the persistence time of MC-RR in cropland soils should be about 6 days. This result also suggested the beneficial effects of the organic fertilizer utilization for the biodegradation of MC-RR in cropland soils. Our studies also demonstrated that MC-RR at low concentration (< 10 mu g/L) could accelerate the growth of plants, while high concentration of MC-RR (> 100 mu g/L) significantly inhibited the growth of plants. High sensitivity of the sprouting stage plants to MC-RR treatments as well as the strong inhibitory effects resulting from prolonged irrigation further indicated that this MC-RR growth-inhibition may vary with the duration of irrigation and life stage of the plants. (c) 2007 Published by Elsevier Ltd.

A laboratory study of rheological properties of mudflows in Hangzhou Bay, China

A laboratory study of the rheology of mudflows in Hangzhou Bay, China, is reported in this paper. Both the steady and oscillatory (dynamic) rheological properties are studied using RMS-605 rheometer. A Dual-Bingham model is proposed for analyzing flow curves and compared with Worrall-Tuliani model. It is found that Dual-Bingham plastic rheological model is easier to implement than Worrall-Tuliani model and can provide satisfactory representations of the steady mudflows in Hangzhou Bay and other published data. The dependence of the yield stress and viscosity on sediment concentration is discussed based on the data from Hangzhou Bay mud and other published data. For the dynamic rheological properties of Hangzhou Bay mud, empirical expressions for elastic modulus and dynamic viscosity are provided in the form of exponential functions of sediment volume concentration, and comparisons with other published data also discussed.

Field and laboratory studies on pathological and biochemical characterization of microcystin-induced liver and kidney damage in the phytoplanktivorous bighead carp

Field and experimental studies were conducted to investigate pathological characterizations and biochemical responses in the liver and kidney of the phytoplanktivorous bighead carp after intraperitoneal (i.p.) administration of microcystins (MCs) and exposure to natural cyanobacterial blooms in Meiliang Bay, Lake Taihu. Bighead carp in field and laboratory studies showed a progressive recovery of structure and function in terms of histological, cellular, and biochemical features. In laboratory study, when fish were i.p. injected with extracted MCs at the doses of 200 and 500 mu g MC- LReq/kg body weight, respectively, liver pathology in bighead carp was observed in a time dose-dependent manner within 24 h postinjection and characterized by disruption of liver structure, condensed cytoplasm, and the appearance of massive hepatocytes with karyopyknosis, karyorrhexis, and karyolysis. In comparison with previous studies on other fish, bighead carp in field study endured higher MC doses and longer-term exposure, but displayed less damage in the liver and kidney. Ultrastructural examination in the liver revealed the presence of lysosome proliferation, suggesting that bighead carp might eliminate or lessen cell damage caused by MCs through lysosome activation. Biochemically, sensitive responses in the antioxidant enzymes and higher basal glutathione concentrations might be responsible for their powerful resistance to MCs, suggesting that bighead carp can be used as biomanipulation fish to counteract cyanotoxin contamination.

花椒的化感作用对凋落物分解的影响及机理研究

花椒（Zanthoxylum bungeanum）是川西干旱河谷地区重要的经济作物，化感作用是花椒连作障碍的重要原因之一。花椒凋落物分解是影响花椒林地土壤肥力及花椒产量的重要因素，因此系统研究花椒化感作用是否对花椒凋落物的分解产生影响可以为解决花椒连作障碍导致的产量下降等问题提供科学的理论依据。本文通过室内模拟实验研究了花椒凋落物的四个分解动态以及分解后凋落物浸提液对花椒林地土壤性质的影响；通过野外盆栽实验研究了花椒凋落物浸提液对花椒幼苗的生长、花椒凋落物的质量及土壤性质的影响。最终从生理生化角度揭示了花椒的化感作用对凋落物分解的影响机理，为深入解决花椒连作障碍问题、对花椒凋落物采取有效的人工措施提供了科学的理论依据。主要的研究结果如下： 1. 室内分解实验证明，花椒凋落物在分解的60 d 内分解速率呈现由大到小的变化趋势，并且凋落物分解呈现明显的毒性动态。凋落物在分解的10 d、30 d 时，分解速率较大，30 d 以后分解速率显著降低。凋落物分解的10 d 左右酚酸释放量最大，此时凋落物的毒性最大，凋落物分解到10 d 以后，酚酸释放量逐渐减少，凋落物的毒性也逐渐减小。 2. 四个分解动态的花椒凋落物浸提液对土壤化学性质产生了显著的影响。花椒凋落物在分解的60 d 内，其浸提液使土壤pH值均显著的增加。分解0 d 的凋落物浸提液显著的降低了土壤铵态氮的含量，抑制了纤维素分解菌的生长；分解60 d 的凋落物浸提液显著的降低了土壤酚酸含量，增加了土壤有效磷的含量；分解30 d 和60 d 的凋落物浸提液均显著的促进了好气性纤维素分解菌的生长。这说明花椒凋落物在分解过程中呈现出明显的毒性动态：凋落物分解的初期毒性作用较大，随着分解的继续进行特别是在分解的30 d 以后，其毒性作用慢慢降低。 3. 花椒凋落物浸提液对花椒幼苗表现出明显的化感作用。不同浓度的浸提液对花椒幼苗地上及地下生物量、叶面积均产生了显著的抑制作用，并且随着浸提液浓度的升高抑制作用加强。凋落物浸提液对叶片厚度的影响较小，只有Y1对叶片厚度的生长抑制作用显著。 4. 花椒的化感作用改变了凋落物的质量，并对凋落物分解产生了显著的影响。对花椒幼苗用不同浓度的凋落物浸提液进行处理，Y1使凋落物有机碳含量、木质素含量、C/N、木质素/氮显著降低，纤维素含量显著升高；Y3使凋落物有机碳含量、木质素含量、C/N、木质素/氮显著升高。花椒凋落物质量的改变显著的影响了凋落物的分解，凋落物的分解速率大小依次为：Y1（10.15 a-1）> Y2（8.71 a-1）> CK（6.41 a-1）> Y3（5.08 a-1）。 5. 花椒的化感作用改变了土壤性质，并对凋落物分解产生了显著的影响。对花椒幼苗用不同浓度的凋落物浸提液处理的同时，也改变了土壤性质。不同浓度的凋落物浸提液显著的升高了土壤pH值、有机碳含量。各种浓度的凋落物浸提液对土壤多酚氧化酶的活性均起到了显著的促进作用。凋落物浸提液Y1对土壤纤维素分解酶的活性、细菌和真菌的生长也具有显著的促进作用。土壤性质的改变显著的影响了凋落物的分解，凋落物的分解速率大小依次为：Y1（10.30 a-1）>Y2（9.60 a-1）>CK（6.41 a-1）>Y3（6.29 a-1）。 6. 不论是凋落物质量发生改变还是土壤性质发生改变，在凋落物分解的整个过程中，C元素始终处于单调净释放的状态，并且C释放量与分解速率成显著的正相关，即凋落物分解越快，凋落物C释放量越大。凋落物分解过程中，均出现了酚酸大量释放的情况，并与凋落物分解速率成显著正相关。凋落物分解后的木质素含量、木质素/氮均增加，并且随着浸提液浓度的升高，凋落物木质素含量、木质素/氮升高。 Zanthoxylum bungeanum is an important economic crop in dry valley of the Minjiang river (Sichuan, Southwest China), but allelopathy is one of the important reasons for its continuous cropping. Zanthoxylum bungeanum litter decomposition affects Zanthoxylum bungeanum soil fertility and its output. So systemically investigate if allelopathy affects litter decomposition could provide the scientific methods to solve the problem of output fall caused by the continuous cropping. In this paper, the releasing dynamics of phenolic acid during Zanthoxylum bungeanum litter decomposition (0, 10, 30 and 60 days) and the effects of its aqueous extract on soil chemical properties were investigated via the laboratory study. Effects of Zanthoxylum bungeanum litter aqueous extract on the growth of young Zanthoxylum bungeanum seedlings, litter qualities and the soil qualities were investigated via the field study. Finally, we open out the action manner of Zanthoxylum bungeanum allelopathic effect on the litter decomposition, and provide the theoretical basis to solve the Zanthoxylum bungeanum continuous cropping. The main results showed that: 1. The laboratory litter decomposition experiment showed a trend of decomposition rate from large to small and an occurrence of phytotoxicity with clear dynamic patterns during Zanthoxylum bungeanum litter decomposition. The litter decomposition rate was larger at the tenth and 30th day during 60-day litter decomposition and gradually decreased after 30 days of litter decompostion. The releasing quantity of the litter phenolic acid was the highest at the tenth day, and here, the litter toxicity was the biggest. The releasing quantity of the litter phenolic acid gradually decreased after 10 days of litter decomposition, so the phytotoxicity of litter was gradually decreased with the litter decomposition. 2. The Zanthoxylum bungeanum litter aqueous extract after four decomposition stages had significantly effect on the soil chemical qualities. The pH value in soil was significantly increased in litter aqueous extract of four decomposition stages. The NH+4-N concentration was significantly decreased in soil amended with litter aqueous extract of 10-day decomposition which inhibited the growth of Aerobic cellulose-decomposer. The growth of soil Aerobic cellulose-decomposer was promoted by the litter aqueous extract of 30-day decomposition. Available phosphorus concentration was significantly increased and phenolic acid content was significantly decreased in soil amended with litter aqueous extract of 60-day decomposition which promoted the growth of Aerobic cellulose-decomposer. The study results showed an occurrence of phytotoxicity with clear dynamic patterns during Zanthoxylum bungeanum litter decomposition. The phytotoxicity of litter was the largest at the initial stage, but the phytotoxicity gradually decreased with the litter decomposition, especially after 30 days of decomposition. 3. The field study indicated that the Zanthoxylum bungeanum litter aqueous extract had significant allelopathic effects on the growth of young seedlings.Different concentration aqueous extract had signinficant inhibiting effects on biomass and leaf area of young seedlings. The inhibiting effect on the biomass strengthened with the litter aqueous extract concentration augment. Litter aqueous extracts had less effect on the leaf thickness, and only Y1 had significant inhibiting effect on the leaf thickness. 4. The Zanthoxylum bungeanum allelopathy had significant effect on the litter qualities and the litter decomposition. Treating the young Zanthoxylum bungeanum seedlings with different concentration of litter aqueous extracts, the leaf litter organic C, lignin, C/N and lignin/N all decreased and the cellulose content increased under Y1 treatment. The leaf litter organic C, lignin, C/N and lignin/N all increased under Y3 treatment. So the litter decomposition was significant affectded by the litter qualities, and the litter decomposition rate was Y1(10.15 a-1)> Y2(8.71 a-1) > CK(6.41 a-1) > Y3(5.08 a-1). 5. The Zanthoxylum bungeanum allelopathy had significant effect on the soil qualities and the litter decomposition. Treating the young Zanthoxylum bungeanum seedlings with different concentration of litter aqueous extracts, also changed the soil qualities. Different concentration of litter aqueous extracts had significant effects on the soil pH and organic C content. Every concentration of litter aqueous extracts accelerated the soil Polyphenol Oxidase activity and Y1 accelerated the soil Cellulase activity, the number of soil bacteria and fungi. So the litter decomposition was significant affected by the soil qualities, and the litter decomposition rate was Y1(10.30 a-1) > Y2 (9.60 a-1) >CK(6.41 a-1)>Y3(6.29 a-1)。 6. Whether the litter or soil qualities changed, the litter C element at the state of release at all times during the litter decomposition, and the release quantity increased with the decomposition rate augment. Litter released plentiful total penolics content during decomposition, and the release quantity had the positive correlation with the litter decomposition rate. The litter lignin content and the lignin/N all increased with the litter aqueous extracts concentration augment after litter decomposition.

Experimental study on pore pressure in rock-soil slope during reservoir water level fluctuation

A test system was developed for measuring the pore pressure in porous media, and a new model was devised for the pore pressure testing in both saturated and unsaturated rock-soil. Laboratory experiments were carried out to determine the pore pressure during water level fluctuation. The variations of transient pore pressure vs. time at different locations of the simulated rock-soil system were acquired and processed, and meanwhile the deformation and failure of the model are observed. The experiment results show that whether the porous media are saturated or not, the transient pore pressure is mainly dependent on the water level fluctuation, and coupled with the variation of the stress field.

Study on the Mechanical Properties of the Tetrahydrofuran Hydrate Deposit

Pure tetrahydrofuran hydrate and tetrahydrofuran hydrate deposits with different materials as the skeleton are synthesized in our laboratory. A series of experiments are carried out to study the mechanical properties. The stress-strain curve, strength of pure tetrahydrofuran hydrate and hydrate deposit are obtained. Some phenomenon is explained.

Experimental Study on the Ignition Process of Single Coal Particles at Microgravity

In this paper, the first Chinese microgravity (μ-g) experimental study on coal combustion was introduced. An experimental system used to study the ignition process of single coal particles was built up, complying with the requirements of the 3.5 s drop tower in the National Microgravity Laboratory of China (NMLC). High volatile bituminous and lignite coal particles with diameter of 1.5 and 2.0 mm were tested. The ignition and combustion process was recorded by a color CCD and the particle surface temperature before and at the ignition was determined by the RGB colorimetric method. Comparative experiments were conducted at normal gravity (1-g). The experiments revealed that at different gravity levels, the ignition of all tested coal particles commenced in homogeneous phase, while the shape, structure, brightness and development of the flames, as well as the volatile matter release during the ignition process are different. At μ-g, the part of volatile was released as a jet, while such a phenomenon was barely observed at 1-g. Also, after ignition, flames were more spherical, thicker, laminated and dimmer at μ-g. It was confirmed that ignition temperature decreased as the particle size or volatile content increased. However, contradicted to existing experimental results, provided other experimental conditions except gravity level were the same, ignition temperature of coal particles was about 50–80 K lower at μ-g than that at 1-g.

Experimental Study on the Responses of Bucket Foundations in Calcareous Sand under Vertical Dynamic Loading

Abstract: Experiments to determine the vertical static bearing capacity are carried out first in laboratory which is taken as a reference for choosing the amplitudes of vertical dynamic loading. Then a series of experiments are carried out to study the influences of factors, such as the scales of bucket, the amplitude and frequency of loading, the density of soils etc.. According to the experimental results, the responses of bucket foundations in calcareous sand under vertical dynamic loadings are analyzed. It is shown that there exists a limited effected zone under vertical dynamic loading. The scale of this zone is about one times of the bucket’s height. In this zone, the density of soil layer, the deformation and the pore pressure change obviously.

Characterization of a fibrinogen-clotting enzyme from Trimeresurus stejnegeri venom, and comparative study with other venom proteases

Trimeresurus stejnegeri venom, which contains TSV-PA (a specific plasminogen activator sharing 60-70% sequence homology with venom fibrinogen-clotting enzymes), also possesses fibrinogen-clotting activity in vitro. A fibrinogen-clotting enzyme (stejnobin) has been purified to homogeneity by gel filtration and ion-exchange chromatography on a Mono-Q column. It is a single-chain glycoprotein with a mol. wt of 44,000. The NH2-terminal amino acid sequence of stejnobin shows great homology with venom fibrinogen-clotting enzymes and TSV-PA. Like TSV-PA, stejnobin was able to hydrolyse several chromogenic substrates. Comparative study of substrate specificities of stejnobin and other venom proteases purified in our laboratory was carried out on five chromogenic substrates. Stejnobin clotted human fibrinogen with a specific activity of 122 NIH thrombin-equivalent units/mg protein. However, stejnobin did not act on other blood coagulation factors, such as factor X, prothrombin and plasminogen. Diisopropyl fluorophosphate and phenylmethanesulfonyl fluoride inhibited its activity, whereas ethylenediamine tetracetic acid had no effect on it, indicating that it is a serine protease. Although stejnobin showed strong immunological cross-reaction with polyclonal antibodies raised against TSV-PA, it was interesting to observe that, unlike the case of TSV-PA, these antibodies did not inhibit the amidolytic and fibrinogen-clotting activities of stejnobin. (C) 1998 Elsevier Science Ltd. All rights reserved.

Mechanism study on the frequent variations of cell-bound microcystins in cyanobacterial blooms in Lake Taihu: Implications for water quality monitoring and assessments

Although Microcystis-based toxins have been intensively studied, previous studies using laboratory cultures of Microcystis strains are difficult to explain the phenomenon that microcystin concentrations and toxin variants in natural blooms differ widely and frequently within a short-term period. The present study was designed to unravel the mechanisms for the frequent variations of intracellular toxins related to the differences in cyanobacterial colonies during bloom seasons in Lake Taihu, China. Monitoring of Microcystis colonies during warm seasons indicated that the variations in microcystins in both concentrations and toxin species were associated with the frequent alteration of Microcystis colonies in Lake Taihu. High concentration of microcystins in the blooms was always associated with two Microcystis colonies, Microcystis flos-aquae and Microcystis aeruginosa, whereas when Microcystis wesenbergii was the dominant colonial type, the toxin production of the blooms was low. Additionally, environmental factors such as temperature and nutrition were also shown to have an effect on the toxin production of the blooms, and may also potentially influence the Microcystis species present. The results of the present study provides insight into a new consideration for quick water quality monitoring, assessment and risk alert in cyanobacterium- and toxin-contaminated freshwaters, which will be beneficial not only for water agencies but also for public health. (C) 2009 Elsevier Ltd. All rights reserved.

Comparative study of estrogenic potencies of estradiol, tamoxifen, bisphenol-A and resveratrol with two in vitro bioassays

This study was undertaken to compare the sensitivity of two in vitro screening test methods and to determine the accuracy of predicted response to spiked laboratory water samples. A newly developed enzyme-linked receptor assay (ELRA) and a widely used yeast estrogen screen (YES) assay were selected to evaluate the estrogenic responses. Four natural, pharmaceutical, xenobiotic or phytobiotic chemicals: 17beta-estradiol (E2), tamoxifen, bisphenol-A and resveratrol were examined, and 17beta-E2 was used as a positive control. 17beta-E2 can strongly induce estrogenic response in both test systems, however, ELRA was found to be more sensitive to 17beta-E2 with a detection limit of 0.07 mug/l compared to 0.88 mug/l in YES assay. Similar results were obtained for bisphenol-A and resveratrol, and their estrogen potencies relative to E2 (100%) determined by ELRA were at least 5.6 times greater than produced by YES assay. ELRA was unable to distinguish the anti-estrogen tamoxifen and YES assay is also poor at distinguishing. Comparison of response to spiked laboratory water samples show that ELRA can give accurate determination to all four chemicals with recoveries among 70-120%, while YES can only give accurate determination to 17beta-E2 and bisphenol-A with recoveries among 69-112%. The comparative results provide evidence that ELRA is more suitable for rapid screening estrogenic potency of the environmental samples. Combination of ELRA and mammalian cellular assay will constitute an advantageous test to specify agonistic or antagonistic effects. (C) 2003 Elsevier Ltd. All rights reserved.

Study of sorption, biodegradation and isomerization of HCH in stimulated sediment/water system

This paper reported the sorption, biodegradation and isomerization of hexachlorocyclohexane (HCH) in laboratory sediment/water system under aerobic and anaerobic conditions, respectively. The effect of organic nutrient addition to the sorption of HCH was also investigated. It indicates that HCH is highly adsorbed on sediments under both conditions. During the tests, the biodegradation and isomerization of HCH were dramatically speeded up after organic nutrient additions, especially in the case of the observation under aerobic condition. It was found, beta-HCH was the most persistent in the environment, that is due to the isomerization of alpha-HCH in a big amount to beta-HCH, besides its chemical stability. (C) 1997 Elsevier Science Ltd.

Study of GaN epilayers growth on freestanding Si cantilevers

Five-micron thick freestanding Si cantilevers were fabricated on bulk Si (1 1 1) substrates with surface/bulk micromachining (SBM) process. Then 1-mu m thick GaN layers were deposited on the Si cantilevers by metal-organic chemical vapor deposition (MOCVD). Epilayers on cantilever areas were obtained crack-free, and the photoluminescence (PL) spectra verified the stress reduction and better material quality in these suspended parts of GaN. Back sides of the cantilevers were also covered with GaN layers, which prevented the composite beams from bending dramatically. This paper had proved the feasibility of integrating high-quality GaN epilayers with Si micromechanical structures to realize GaN-based micro electro-mechanical system (MEMS). (C) 2009 Elsevier Ltd. All rights reserved.