西江肇庆江段鱼类早期资源时空分布特征研究

2006年5～7月对西江肇庆江段鱼苗的时空分布进行了研究,结果表明:5月17日及6月1日前后该江段有苗汛发生,鱼苗密度平均值为0.83尾/m3,最大值为7.9尾/m3;鱼苗密度昼夜分布有显著性差异(n=26,P<0.01),夜间的密度比白天的高;鱼苗的种类在昼夜分布上也有明显差异,四大家鱼鱼苗的分布主要集中于夜间;鱼苗的分布具空间差异性,近岸的鱼苗密度高于江中央的。

膜生物反应器稳定运行的操作条件优化研究

膜污染是限制膜生物反应器(MBR)应用和发展的瓶颈。为此,选择污泥浓度、膜通量(JV)、曝气量(Q气)、抽吸/停抽时间(tR/tS)、反应器升流区与降流区面积之比(Ar/Ad)进行正交试验,开展了MBR操作条件的优化研究。结果表明,溶解性胞外多聚物是导致膜污染形成和发展的主要物质,其中蛋白质/多糖值与膜压差上升速率存在线性关系;较佳的操作参数为:MLSS=7g/L,JV=10 L/(m2.h),Q气=6 m3/h,tR/tS=4 min/1 min,Ar/Ad=1.7。

人工湿地组合工艺对水体中浮游动物群落结构的影响

研究了在不同水力负荷条件下[0.6 m3.(m2.d)-1,0.8 m3.(m2.d)-1,1.0 m3.(m2.d)-1],人工湿地组合工艺系统对浮游动物群落结构的影响和在相同的水力负荷下,人工湿地组合工艺系统对浮游动物群落结构影响的季节性变化.结果表明,在水力冲击负荷为0.8 m3.(m2.d)-1时对浮游动物群落结构的影响相对较大;春、夏、秋季的作用强于冬季,而秋季对浮游动物群落结构的影响最大;对大型浮游动物的影响大(去除率≥70%),对小型浮游动物的影响相对小一些,湿地出水中出现了一些进水中没有的

滇池摇蚊科幼虫和水丝蚓属的生物学特性分析

报道了昆明滇池摇蚊科幼虫Chironomidae、水丝蚓属Limnodrilus的分类特征、生态学特点 ,分析了滇池摇蚊科幼虫、水丝蚓属优势种的变化及与滇池水质的关系 ;首次对其食性进行了分析并对其摄食量进行了估算 ,研究结果表明 :1kg摇蚊幼虫每天可消耗鲜藻 0 0 94kg ;1kg水蚯蚓每天可消耗鲜藻 0 0 89kg ;讨论了摇蚊幼虫、水丝蚓在昆明滇池综合治理中起到的控藻作用 ,为滇池的综合治理提供了基础资料。

围隔中鲢和菹草控藻效果及其生态学意义

在滇池沿岸的池塘中 ,构建了面积为 10 0m2 ,水深为 85cm ,底质均为淤泥的四个围隔 ,其中在三个围隔内分别放养密度为 10 0g/m3 、75g/m3 、5 0g/m3 的鲢。它们均在一定程度上控制浮游植物的生物量并改善水体透明度 ,其中初始放养鲢 75g/m3 的围隔控制效果最明显。放养三种密度的鲢在有效控制微囊藻水华的同时 ,原先水体的优势种类发生质的变化 ,水体中浮游植物的多样性也明显增加。放鱼 2个月后 ,在生物操纵的围隔中同时种入菹草 ,在75g/m3 的鲢控藻的围隔中 ,菹草长势良

汉江中下游江段藻类现状调查及“水华”成因分析

汉江是长江的最大支流,全长1532km,年径流总量为591亿m3,流域面积15.1万km2。汉江既是湖北省主要航道之一,又是沿岸居民生活用水和工业用水的重要水源。早在70年代,汉江的水质一直符合地面水II级标准,但自90年代以来,汉江的水质逐年下降,并分别于1992年和1998年的初春先后两次发生硅藻大量繁殖,水色发褐并伴有异味。本文在调查汉江中、下游江段藻类现状的基础上,对硅藻猛增并出现水华征兆的成因进行了分析,结果显示,在汉江中、下游的纳污江段及河湾处,水质污染问题十分严峻,其中汉江下游江段的水质比中

Inhibition of no tail (ntl) gene expression in zebrafish by external guide sequence (EGS) technique

External guide sequence (EGS) technique, a branch of ribozyme strategy, can be enticed to cleave the target mRNA by forming a tRNA-like structure. In the present study, no tail gene (ntl), a key gene participating in the formation of normal tail, was used as a target for ribonuclease (RNase) P-mediated gene disruption in zebrafish in vivo. Transient expression of pH1-m3/4 ntl-EGS or pH1-3/4 ntl-EGS produced the full no tail phenotype at long-pec stage in proportion as 24 or 35%, respectively. As is expected that the full-length ntl mRNA of embryos at 50% epiboly stage decreased relative to control when injected the embryos with 3/4 EGS or m3/4 EGS RNA. Interestingly, ntl RNA transcripts, including the cleaved by EGS and the untouched, increased. Taken together, these results indicate that EGS strategy can work in zebrafish in vivo and becomes a potential tool for degradation of targeted mRNAs.

Mechanics of biological networks: from the cell cytoskeleton to connective tissue.

From the cell cytoskeleton to connective tissues, fibrous networks are ubiquitous in metazoan life as the key promoters of mechanical strength, support and integrity. In recent decades, the application of physics to biological systems has made substantial strides in elucidating the striking mechanical phenomena observed in such networks, explaining strain stiffening, power law rheology and cytoskeletal fluidisation - all key to the biological function of individual cells and tissues. In this review we focus on the current progress in the field, with a primer into the basic physics of individual filaments and the networks they form. This is followed by a discussion of biological networks in the context of a broad spread of recent in vitro and in vivo experiments.

Influence of turbulence-chemistry interaction for n-heptane spray combustion under diesel engine conditions with emphasis on soot formation and oxidation

The influence of the turbulence-chemistry interaction (TCI) for n-heptane sprays under diesel engine conditions has been investigated by means of computational fluid dynamics (CFD) simulations. The conditional moment closure approach, which has been previously validated thoroughly for such flows, and the homogeneous reactor (i.e. no turbulent combustion model) approach have been compared, in view of the recent resurgence of the latter approaches for diesel engine CFD. Experimental data available from a constant-volume combustion chamber have been used for model validation purposes for a broad range of conditions including variations in ambient oxygen (8-21% by vol.), ambient temperature (900 and 1000 K) and ambient density (14.8 and 30 kg/m3). The results from both numerical approaches have been compared to the experimental values of ignition delay (ID), flame lift-off length (LOL), and soot volume fraction distributions. TCI was found to have a weak influence on ignition delay for the conditions simulated, attributed to the low values of the scalar dissipation relative to the critical value above which auto-ignition does not occur. In contrast, the flame LOL was considerably affected, in particular at low oxygen concentrations. Quasi-steady soot formation was similar; however, pronounced differences in soot oxidation behaviour are reported. The differences were further emphasised for a case with short injection duration: in such conditions, TCI was found to play a major role concerning the soot oxidation behaviour because of the importance of soot-oxidiser structure in mixture fraction space. Neglecting TCI leads to a strong over-estimation of soot oxidation after the end of injection. The results suggest that for some engines, and for some phenomena, the neglect of turbulent fluctuations may lead to predictions of acceptable engineering accuracy, but that a proper turbulent combustion model is needed for more reliable results. © 2014 Taylor & Francis.

Electrical control of nanoscale functionalization in graphene by the scanning probe technique

Functionalized graphene is a versatile material that has well-known physical and chemical properties depending on functional groups and their coverage. However, selective control of functional groups on the nanoscale is hardly achievable by conventional methods utilizing chemical modifications. We demonstrate electrical control of nanoscale functionalization of graphene with the desired chemical coverage of a selective functional group by atomic force microscopy (AFM) lithography and their full recovery through moderate thermal treatments. Surprisingly, our controlled coverage of functional groups can reach 94.9% for oxygen and 49.0% for hydrogen, respectively, well beyond those achieved by conventional methods. This coverage is almost at the theoretical maximum, which is verified through scanning photoelectron microscope measurements as well as first-principles calculations. We believe that the present method is now ready to realize 'chemical pencil drawing' of atomically defined circuit devices on top of a monolayer of graphene. © 2014 Nature Publishing Group All rights reserved.

Effect of feeding frequency on growth, feed utilization, and size variation of juvenile gibel carp (Carassius auratus gibelio)

Juvenile (3.0 +/- 0.2 g) gibel carp (Carassius auratus gibelio ) were fed to satiation for 8 weeks to investigate the effect of feeding frequency on growth, feed utilization and size variation. Five feeding frequencies were tested: two meals per day (M2), three meals per day (M3), four meals per day (M4), 12 meals per day (M12) and 24 meals per day (M24). The results showed that daily food intake increased significantly with the increase in feeding frequency and there was no significant difference between daily food intakes in M12 and M24 treatments. Growth rate, feed efficiency increased significantly with increasing feeding frequencies. Size variation was not affected by feeding frequency. Apparent digestibility of dry matter was not influenced by feeding frequency, while apparent digestibility of protein and energy increased significantly at high feeding frequencies. The feeding frequency had no significant effect on the moisture, lipid, protein, or energy contents of gibel carp, while the ash content decreased with increased feeding frequency. It was recommended that 24 meals per day was the optimal feeding frequency for juvenile gibel carp.

PLANKTON AND SESTON STRUCTURE IN A SHALLOW, EUTROPHIC SUBTROPICAL CHINESE LAKE

The seasonal dynamics in the nutrient concentrations, chlorophyll-a amount (Chl-a), total algal volume (CV), Chl-a/CV ratio, seston structure were studied at two sampling stations in a shallow, highly eutrophicated subtropic lake (the Guozheng Hu area of the East Lake) on the plain of the middle basin of the Chang Jiang (the Yangtze River) of China. The lake ecosystem of the Guozheng Hu area is dominated by two planktivorous fishes (silver carp and bighead carp), phytoplankton and zooplankton. Macrophytes are extremely scarce in this area. Concentrations of the total dissolved nitrogen and phosphorus in the Guozheng Hu area in 1990 were very high. Fish yield, of which, more than 90 % was composed of silver carp and bighead carp in the Guozheng Hu area was very high (ca. 1140 kg/ha or 45.6 g/m3 in 1990). Grazing pressure by the fishes on the plankton community is considered to be rather strong. The annual average biomass of zooplankton was ca. 1/3 - 1/2 that of phytoplankton. On the average, dry matter in the living plankton only constituted ca. 3-7 % of the total dry seston, and plankton carbon only constituted ca. 5 - 10 % of the seston carbon. The present results indicate that, in the Guozheng Hu area of the East Lake, of the organic part of the seston, detritus is quantitatively an important constituent, while living plankton is only a very small component.

ROLE OF PHOSPHORUS CYCLING IN ALGAL METABOLISM AND ALGAL SUCCESSION IN LAKE DONGHU, CHINA

The role of phosphorus cycling in algal metabolism was studied in a shallow lake, Donghu, in Wuhan using the methods of measuring cell quota C, N and P, and calculating nutrients uptake rate by algal photosynthesis. The mean daily phosphorus uptake rate of phytoplankton varied between 0.04-0.11 and 0.027-0.053 g/m2/d in station I and station II respectively. The turnover time of phosphorus in phytoplankton metabolism ranged from 0.75-5.0 days during 1979-1986. The available P was 0.176 (+/- 0.156) g/m3 (mean +/- SD) in 1982 and 0.591 (+/- 0.24) g/m3 in 1986. The relationship between P/B ratio (Y) and TP (X: mg/l) was described by the following regression equation Y = 1.163 + 0.512logX (r = 0.731, P < 0.001). The dynamics of algal biomass and algal species succession were monitored as the indicators of environmental enrichment. The small-sized algae have replaced the blue-green algae as the dominant species during 1979-1986. The small-sized algae include Merismopedia glauca, Cryptomonas ovata, Cryptomonas erosa, several species Cyclotella. There has been drastic decrease in algal biomass and an obvious increase in P/B ratio. A nutrient competition hypothesis is proposed to explain the reason of the disappearance of blue-green algae bloom. The drastic change in algal size and the results in high P/B ratio (reaching a maximum mean daily ratio of 1.09 in 1986) may suggest a transition of algal species from K-selection to r-selection in Lake Donghu.

可信计算环境证明方法研究

首先分析了可信计算环境下多远程证明实例执行的动态性、并发性、一致性等问题，提出了一个完整的可信计算环境多远程证明实例动态更新证明方案，以保证通信双方终端计算环境的可信。然后阐述了主要由计算环境组件度量算法、会话组件树计算算法和多远程证明实例证明协议组成可信计算环境证明方法。最后对该证明方法的安全性和效率进行分析，并构建原型系统论证证明方案的可行性和高性能。

移动对象数据库模型、查询语言及实时交通流分析

提出一种移动对象数据库模型——Dynamic Transportation Network Based Moving Objects Database(简称DTNMOD),并给出了DTNMOD中基于移动对象时空轨迹的网络实时动态交通流分析方法.在DTNMOD中,交通网络被表示成动态的时空网络,可以描述交通状态、拓扑结构以及交通参数随时间的变化过程;网络受限的移动对象则用网络移动点表示.DTNMOD模型包含了完整的数据类型和查询操作的定义,因此可以在任何可扩充数据库(如PostgreSQL或SECONDO)中实现,从而得到完整的数据库模型和查询语言.为了对相关模型的性能进行比较与分析,基于PostgreSQL实现了一个原型系统并进行了一系列的实验.实验结果表明,DTNMOD提供了良好的区域查询及连接查询性能.