基于复合垂直流人工湿地的循环水养殖系统净化养殖效能与参数优化

该文对基于复合垂直流人工湿地(IVCW)的循环水养殖系统的净化效率、养殖效果和系统优化设计进行了研究。结果表明,在420 mm/d的水力负荷下,湿地可有效地去除循环水中的总悬浮物(去除率85%)、CODCr(去除率50%)、BOD5(去除率44%)、总氨氮(去除率53%)、亚硝酸盐(去除率83%)和硝酸盐(去除率54%),能够满足养殖用水的要求,整个试验期间系统实现了零污水排放。经过5个月的养殖,成功地将斑点叉尾鮰(Ictalurus punctatus)鱼苗(1.8 cm,0.08g)培育成鱼种(15.

滇池藻类生物量时空分布及其影响因子

以滇池全湖选取的40个样点,从2001年9月到2002年8月对全湖水体中的叶绿素a的含量每月进行调查,对浮游植物的群落组成和细胞数每两个月进行分析。结果显示,叶绿素a的含量(月均值)从2002年1月的0.015mg/L增加到2002年8月的0.10mg/L呈现明显的上升趋势,水体温度也从1月的10℃上升到8月的28℃;叶绿素a含量的全湖均值则显示出南部水域低,北部水域高的态势,其中又以1号位点最高。滇池地区常年盛行的西南风导致藻类向北的水平运动加强对这一结果的形成有着重要的影响。种群优势度的结果也显示出蓝

The load-bearing duct: Biomimicry in structural design

The philosophical aspects of applying the principles of biomimicry are explored in a case study of structural design. Integrating structural engineering with services engineering can be regarded, to some extent, as taking principles from biological systems and applying them to large-scale conceptual design. The end-product discussed herein a so-called load-bearing duct, a functional naturally ventilated multi-storey office building that takes the applied loading efficiently both structurally and cost-effectively giving it the potential to be sustainable throughout its design life.

Structural and optical properties of III-V nanowires and nanowire heterostructures grown by metalorganic chemical vapour deposition

We have investigated the structural and optical properties of III-V nanowires grown by metalorganic chemical vapour deposition. Binary GaAs, InAs and InP nanowires, and ternary InGaAs and AlGaAs nanowires, have been fabricated and characterised. A variety of axial and radial heterostructures have also been fabricated, including GaAs/AlGaAs core-multishell and GaAs/InGaAs superlattice nanowires. GaAs/AlGaAs core-shell nanowires exhibit strong photoluminescence as the AlGaAs shell passivates the GaAs nanowire surface reducing the surface nonradiative recombination. © 2007 IEEE.

葡萄藻三个品系脂类物质含量的比较研究

<正> 葡萄藻作为一种新的再生性能源的研究,已引起了不少学者的重视。其中较为关键的是对葡萄藻所含脂类物质的研究。过去通常采用重量法及各类色谱法测定植物中的脂类物质。这些方法不但繁琐,而且均需一个较长时间的提取过程。近年来国外采用一种新型染料——尼罗

鱼类肠肾虫一新种

<正> 1986年6月,作者在四川涪陵的中华倒刺鲃(Barbodes sinensis Bleeker)后肠检获一种纤毛虫,根据虫体的特征及前人的分类方法,鉴定为斜口科(Plagiotomidae),肠肾虫属(Nyctotherus)一新种,定名为长江肠肾虫(Nyctotherus changjiangensis sp.nov.) 寄生虫的形态研究,除活体观察外,均采用纤毛虫常规涂片染色方法观察。测量了10个以上标本,测量单位为微米。模式标本保存于中国科学院水生生物研究所鱼病室。长江肠肾虫(新种)Nyct

宜昌鳅鮀仔稚鱼的形态特征

<正> 宜昌鳅(鱼它)系底栖性小型鱼类,在长江宜昌江段的渔获物中时有出现。繁殖期为5—6月,产漂流性卵,膜径在3.1—4.0毫米之间,水温21.2—25℃时,受精卵约经40小时孵出。作者对其仔稚鱼的形态进行了观察。实验材料系长江宜都江段采得的天然受精卵,经室内孵化培养而成的仔稚鱼。选择一尾经乌拉坦(ureathane)麻醉后在解剖镜下测量身体各部比例,记述形态特征,并绘制草图。另选两尾作对照。开始摄食后,以浮游生物喂养,培育至外

A single FBAR-based temperature and pressure sensors

A novel temperature and pressure sensor based on a single film bulk acoustic resonator (FBAR) is designed. This FBAR support two resonant modes, which response opposite to the change of temperature. By sealed the back cavity of a back-trench membrane type FBAR with silicon wafer, an on-chip single FBAR sensor suitable for measuring temperature and pressure simultaneously is proposed. For unsealed device, the experimental results show that the first resonant mode has a temperature coefficient of frequency (TCF) of 69.5ppm/K, and the TCF of the second mode is -8.1ppm/K. After sealed the back trench, it can be used as a pressure sensor, the pressure coefficient of frequency (PCF) for the two resonant mode is -17.4ppm/kPa and -6.1 ppm/kPa respectively, both of them being more sensitive than other existing pressure sensors. © 2013 Trans Tech Publications Ltd, Switzerland.

Empirical modelling of submersed macrophytes in Yangtze lakes

Submersed macrophytes in Yangtze lakes have experienced large-scale declines due to the increasing human activities during past decades. To seek the key factor that affects their growth, monthly investigations of submersed macrophytes were conducted in 20 regions of four Yangtze lakes during December, 2001-March, 2003. Analyses based on annual values show that the ratio of Secchi depth to mean depth is the key factor (50% of macrophyte biomass variability among these lakes is statistically explained). Further analyses also demonstrate that the months from March to June are not only the actively growing season for most macrophytes, but the key time the factor acts. Five key-time models yielding higher predictive power (r(2) reaches 0.75,0.76,0.77,0.69 and 0.81) are generated. A comparison between key-time models and traditional synchronic ones indicates that key-time models have higher predictive power. Analyses of transparency thresholds during macrophyte growing season and the limitations of the models are presented. The models and other results may benefit the work concerning submersed macrophyte recovery in Yangtze lakes. (c) 2005 Elsevier B.V. All rights reserved.

Toxicity of cypermethrin on growth, pigments, and superoxide dismutase of Scenedesmus obliquus

Cypermethrin is a synthetic pyrethroid that is particularly toxic to crustaceans. It is therefore applied as a chemotherapeutant in farms for the treatment of pests. The effective concentrations of cypermethrin on the inhibition of Scenedesmus ohliquus growth at 96h (96h EC50) were determined to be 50, 100, 150, 200, and 250mg/L. Algal growth, pigment fractions, and the activity of superoxide dismutase (SOD) in the algal cells were measured in the exponential phase after exposure to cypermethrin. The results show that higher concentration of cypermethrin is inhibitory for growth and other metabolic activities and the 96h EC50 of cypermethrin to S. ohliquus is 112 +/- 9 mg/L; the potential application of SOD activity in S. ohliquus as a sensitive biomarker for cypermethrin exposure is also discussed. (C) 2004 Elsevier Inc. All rights reserved.

Persistent organic pollutants in water and surface sediments of Taihu Lake, China and risk assessment

Organic pollutants, especially persistent organic pollutants were examined in the water and surface sediments of Taihu Lake, China. Both 12 water and 12 sediment samples were collected over the lake. C-18 solid-phase extraction technique was applied to extract organic pollutants in collected water samples. Soxhlet extraction procedure was used to extract organic pollutants in sediment samples. The analysis was performed by GC-MS controlled by a Hewlett Packard chemstation. Two hundred and seventy-three kinds of organic chemicals in water were examined, 200 more than that detected in 1985; 188 kinds of chemicals in sediments were detected as well. Among them 21 kinds of chemicals belong to priority pollutants as well as 17 kinds to be the endocrine disruptors. The concentrations of the pollutants were more than 2 times higher than that in 1985. The possible source and relation to anthropogenic activity were discussed. (C) 2002 Elsevier Science Ltd. All rights reserved.

Growth of juvenile Chinese sturgeon Acipenser sinensis fed live and formulated diets

Triplicate groups of 3.8-g juvenile Chinese sturgeon Acipenser sinensis were reared for 8 weeks in indoor flow-through systems on one of four diets: a natural diet consisting solely of live tubificid worms, a semimoist practical diet, a dry practical diet, and a purified diet. The formulated diets were prepared in the laboratory and had protein contents of 47-50%. Except for the group fed the purified diet, fish showed high survival (94-96%) and growth (final weight, 41-45 g). Survival and specific growth rate did not differ significantly between groups fed the natural, semimoist, and dry practical diets, but were significantly (P < 0.05) lower in fish fed the purified diet. Proximate analysis showed that fish fed purified diet had lower protein and lipid levels but a higher moisture content than fish fed other diets. Our results demonstrated that growth and survival of cultured juvenile Chinese sturgeon fed practical diets were comparable with those fed live tubificid worms. However, Chinese sturgeon fed a purified diet showed inferior growth and survival.

First-principles study of ground-state properties and high pressure behavior of ThO2

The mechanical properties, electronic structure and phonon dispersion of ground state ThO2 as well as the structure behavior up to 240 GPa are studied using first-principles density-functional theory. Our calculated elastic constants indicate that both the ground-state fluorite structure and high pressure cotunnite structure of ThO2 are mechanically stable. The bulk modulus, shear modulus, and Young's modulus of cotunnite ThO2 are all smaller by approximately 25% compared with those of fluorite ThO2. The Poisson's ratios of both structures are approximately equal to 0.3 and the hardness of fluorite ThO2 is 22.4 GPa. The electronic structure and bonding nature of fluorite ThO2 are fully analyzed, and show that the Th-O bond displays a mixed ionic/covalent character. The phase transition from the fluorite to cotunnite structure is calculated to occur at the pressure of 26.5 GPa, consistent with recent experimental measurement by ldiri et al. [1]. For the cotunnite phase it is further predicted that an isostructural transition takes place in the pressure region of 80-130 GPa.

The diphasic nc-Si/a-Si : H thin film with improved medium-range order

A series of silicon film samples were prepared by plasma enhanced chemical vapor deposition (PECVD) near the threshold from amorphous to nanocrystalline state by adjusting the plasma parameters and properly increasing the reactions between the hydrogen plasma and the growing surface. The microstucture of the films was studied by micro-Raman and Fourier transform infrared (FTIR) spectroscopy. The influences of the hydrogen dilution ratio of silane (R-H = [H-2]/[SiH4]) and the substrate temperature (T-s) on the microstructural and photoelectronic properties of silicon films were investigated in detail. With the increase of RH from 10 to 100, a notable improvement in the medium-range order (MRO) of the films was observed, and then the phase transition from amorphous to nanocrystalline phase occurred, which lead to the formation of diatomic hydrogen complex, H-2* and their congeries. With the increase of T-s from 150 to 275 degreesC, both the short-range order and the medium range order of the silicon films are obviously improved. The photoconductivity spectra and the light induced changes of the films show that the diphasic nc-Si/a-Si:H films with fine medium-range order present a broader light spectral response range in the longer wavelength and a lower degradation upon illumination than conventional a-Si:H films. (C) 2004 Elsevier B.V. All rights reserved.

Optical properties and exciton localization in GaNas/GaAs

GaNAs/GaAs single quantum wells (SQWs) and dilute GaNAs bulk grown by molecular beam epitaxy(MBE) were studied by photoluminescence (PL), selectively-excited PL, and time-resolved PL. Exciton localization and delocalization were investigated in detail. Under short pulse laser excitation, the delocalization exciton emission was revealed in GaNAs/GaAs SQWs. It exhibits quite different optical properties from N-related localized states. In dilute GaNAs bulk, a transition of alloy band related recombination was observed by measuring the PL dependence on temperature and excitation intensity and time-resolved PL, as well. This alloy-related transition presents intrinsic optical properties. These results are very important for realizing the abnomal features of III-V-N semiconductors.