早熟河蟹的养殖生态学及其渔业价值评价

把池塘育成的早熟河蟹（即一秋龄性腺成熟中华绒螯蟹）放养于湖汊，其群体越冬成活率为11％。在第二年养殖期间，早熟河蟹不脱壳，体重维持在原来的水平，对鱼肉的日摄食率最高为1．2％，个体不断死亡，至7月中旬，群体全部死完。从当年11月下旬到第二年7月上旬，早熟河蟹成活率曲线公式为：Y=1．09exp（－0018t）［Y：成活率（％），t：时间（d）］。本文还通过对围栏湖汊和扁担塘早熟河蟹逐月跟踪采样、对同龄的末成熟与成熟河蟹的行为及离水成活时间进行对比观察。作者认为，草型湖泊中早熟河蟹没有养殖价值，但若在第二年

Microheterogeneous Thoria-Urania Fuels for Pressurized Water Reactors

A thorium-based fuel cycle for light water reactors will reduce the plutonium generation rate and enhance the proliferation resistance of the spent fuel. However, priming the thorium cycle with ²³⁵U is necessary, and the ²³⁵U fraction in the uranium must be limited to below 20% to minimize proliferation concerns. Thus, a once-through thorium-uranium dioxide (ThO2-UO2) fuel cycle of no less than 25% uranium becomes necessary for normal pressurized water reactor (PWR) operating cycle lengths. Spatial separation of the uranium and thorium parts of the fuel can improve the achievable burnup of the thorium-uranium fuel designs through more effective breeding of ²³³U from the ²³²Th. Focus is on microheterogeneous fuel designs for PWRs, where the spatial separation of the uranium and thorium is on the order of a few millimetres to a few centimetres, including duplex pellet, axially microheterogeneous fuel, and a checkerboard of uranium and thorium pins. A special effort was made to understand the underlying reactor physics mechanisms responsible for enhancing the achievable burnup at spatial separation of the two fuels. The neutron spectral shift was identified as the primary reason for the enhancement of burnup capabilities. Mutual resonance shielding of uranium and thorium is also a factor; however, it is small in magnitude. It is shown that the microheterogeneous fuel can achieve higher burnups, by up to 15%, than the reference all-uranium fuel. However, denaturing of the ²³³U in the thorium portion of the fuel with small amounts of uranium significantly impairs this enhancement. The denaturing is also necessary to meet conventional PWR thermal limits by improving the power share of the thorium region at the beginning of fuel irradiation. Meeting thermal-hydraulic design requirements by some of the microheterogeneous fuels while still meeting or exceeding the burnup of the all-uranium case is shown to be potentially feasible. However, the large power imbalance between the uranium and thorium regions creates several design challenges, such as higher fission gas release and cladding temperature gradients. A reduction of plutonium generation by a factor of 3 in comparison with all-uranium PWR fuel using the same initial ²³⁵U content was estimated. In contrast to homogeneously mixed U-Th fuel, microheterogeneous fuel has a potential for economic performance comparable to the all-UO2 fuel provided that the microheterogeneous fuel incremental manufacturing costs are negligibly small.

武汉东湖浮游动物对浮游细菌的牧食力研究

利用３５μｍ、６４μｍ、９０μｍ和３６０μｍ等不同大小孔径的筛绢网过滤湖水进行了浮游动物对浮游细菌牧食力的研究。结果表明，东湖浮游动物对浮游细菌总滤过率为１８０．１９ｍｌｌ￣（－１）ｈ￣（－１）．摄食率为０．４０μｇＣｌ￣（－１）ｈ￣（－１）。９０μｍ以下的个体为原生动物和轮虫，它们组成了群落总生物量的７５％，其对细菌的牧食力占总牧食力的４４．８％，大于３６０μｍ的浮游动物（主要是甲壳动物）的牧食力占总牧食力的３５．１％。大于９０到小于３６０μｍ的浮游动物其牧食力最小，只占总牧食力的２０％。文中分别用滤过

Statistics anxiety, trait anxiety, learning behavior, and academic performance

The present study investigated the relationship between statistics anxiety, individual characteristics (e.g., trait anxiety and learning strategies), and academic performance. Students enrolled in a statistics course in psychology (N=147) filled in a questionnaire on statistics anxiety, trait anxiety, interest in statistics, mathematical selfconcept, learning strategies, and procrastination. Additionally, their performance in the examination was recorded. The structural equation model showed that statistics anxiety held a crucial role as the strongest direct predictor of performance. Students with higher statistics anxiety achieved less in the examination and showed higher procrastination scores. Statistics anxiety was related indirectly to spending less effort and time on learning. Trait anxiety was related positively to statistics anxiety and, counterintuitively, to academic performance. This result can be explained by the heterogeneity of the measure of trait anxiety. The part of trait anxiety that is unrelated to the specific part of statistics anxiety correlated positively with performance.

转基因鱼模型的建立

本研究运用显微注射方法,把带有小鼠重金属螯合蛋白(MT-1)基因启动顺序与人生长激素基因顺序的重组DNA片段,注入鲤鱼、鲫鱼和泥鳅等的受精卵内,在由此发育的受体中,50％以上整合了外源基因,成为转基因鱼。其中约有一半左右的转基因个体具有表达外源基因、合成人生长激素的能力,并显示出不同程度的快速生长效应。转基因鱼已通过有性生殖将外源基因传递给子代,后者亦具有表达人生长激素的能力。至此,本研究首次建立了一个高效、简洁而且完整的转基因鱼模型,它为鱼类基因工程定向育种新技术奠定了实验基础。同时,本文还就鱼类基因转

广西鲤科鱼类二新种

<正> 1981—1983年,我们在拍摄、编写《中国淡水鱼类原色图集》时,从广西采集一批鱼类标本,经鉴定其中有二新种。正模标本,编号83-IV-0388,全长183毫米,体长147毫米。副模标本7尾,编号83-IV-0008,83-IV-0085,83-IV-0384-0387,83-IV-0389,全长152一227毫米,体长121一184毫米。

Parametrically excited MEMS vibration energy harvesters with design approaches to overcome the initiation threshold amplitude

Resonant-based vibration harvesters have conventionally relied upon accessing the fundamental mode of directly excited resonance to maximize the conversion efficiency of mechanical-to-electrical power transduction. This paper explores the use of parametric resonance, which unlike the former, the resonant-induced amplitude growth, is not limited by linear damping and wherein can potentially offer higher and broader nonlinear peaks. A numerical model has been constructed to demonstrate the potential improvements over the convention. Despite the promising potential, a damping-dependent initiation threshold amplitude has to be attained prior to accessing this alternative resonant phenomenon. Design approaches have been explored to passively reduce this initiation threshold. Furthermore, three representative MEMS designs were fabricated with both 25 and 10 μm thick device silicon. The devices include electrostatic cantilever-based harvesters, with and without the additional design modification to overcome initiation threshold amplitude. The optimum performance was recorded for the 25 μm thick threshold-aided MEMS prototype with device volume ∼0.147 mm3. When driven at 4.2 ms -2, this prototype demonstrated a peak power output of 10.7 nW at the fundamental mode of resonance and 156 nW at the principal parametric resonance, as well as a 23-fold decrease in initiation threshold over the purely parametric prototype. An approximate doubling of the half-power bandwidth was also observed for the parametrically excited scenario. © 2013 IOP Publishing Ltd.

甲基睾丸酮诱导鲫鱼雌核发育子代性转化的研究

本文介绍了用甲基睾丸酮诱导鲫鱼雌核发育子代性转化的研究结果。对孵化后3天的人工雌核发育的红鲫仔鱼和天然雌核发育的银鲫仔鱼,以含有不同量的甲基睾丸酮激素饵料喂养90天,再用一般饵料喂养直到可以剖腹鉴别性别。结果是:1,喂用每克 MT_(25-30μg)激素饵料的,除 1尾发育为精卵巢外.全部试验鱼都发育成雄性;2,喂用每克含 MT_(50-100μg)激素饵料的,没有雄性鱼出现。此外,用 1ml 工业酒精同 1g饵料配制的混合饵料,喂养90天的试验鱼,有60—84.6％的个体发育成雄性。不加激素和酒精的饵料

Ultrastructure of the Spermatozoa of the Yangtze Finless Porpoise (Neophocaena phocaenoides asiaeorientalis)

P>Semen sample was collected from two captive adult Yangtze finless porpoises (Neophocaena phocaenoides asiaeorientalis) during physical examination. One individual was aged about 9 years with body length 143 cm (total length) and body weight 46.1 kg in 2003. The age of the other was unknown and its body length was 147 cm and body weight was 43 kg in 2004. Ultrastructure of their spermatozoa was examined using scanning and transmission electron microscope. The sperm concentration was 4.17 x 10(9) spermatozoa per ml by the cytometer. The approximate dimensions of the spermatozoa were as follows: head length, 3.366 +/- 0.140 mu m (mean +/- SE, n = 15); head width, 1.896 +/- 0.099 mu m (n = 15); and neck length, 1.004 +/- 0.074 mu m (n = 10). The tail included midpiece, principal piece and terminal piece. The length of the midpiece was 1.882 +/- 0.077 mu m (n = 9). There is no apparent boundary between the principal piece and the terminal piece, so the length of the principal piece and the terminal piece was 44.612 +/- 3.485 mu m (n = 5). Total length of the spermatozoa was 53.314 +/- 4.580 mu m (n = 10). The acrosome covered approximately 45.8% of the anterior portion of the head.

Molecular cloning and characterization analysis of immunoglobulin M heavy chain gene in European eel (Anguilla anguilla)

In this study, the immunoglobulin M heavy chain gene of European eel (Anguilla anguilla) was cloned and analyzed. The full-length cDNA of the IgM heavy chain gene (GenBank accession no. EF062515) has 2089 nucleotides encoding a putative protein of 581 amino acids. The IgM heavy chain was composed of leader peptide (L), variable domain (VH), CH1, CH2. Hinge, CH3, CH4, and C-terminus and two novel continuous putative N-glycosylation sites were found close to the second cysteine of CH3 in A. anguilla-H1 and A. anguilla-H2. The deduced amino acid sequence of the European eel IgM heavy chain constant region shared similarities to that of the Ladyfish (Elops saurus). Atlantic salmon (Salmo salar), rainbow trout (Oncorhynchus mykiss), Grass carp (Ctenopharingodon idella), Common carp (Cyprinus carpio), Channel catfish (Ictalurus punctatus), and the orange-spotted grouper (Epinephelus coioides) with the identity of 46.1%, 39.7%, 38.9%, 32.4%, 32.3%, 31.7%, and 30.7%, respectively. The highest level of IgM gene expression was observed in the kidney, followed by the spleen, gills, liver, muscle and heart in the apparently healthy European eels. (C) 2008 Elsevier B.V. All rights reserved.

Developmental expression of CagMdkb during gibel carp embryogenesis

Midkine (Mdk) genes have been revealed to have different expression patterns in vertebrates and therefore, additional studies on Mdk expression patterns are required in more species. In this study, CagMdkb has been cloned and characterized from a SMART cDNA library of 10-somite stage embryos of Carassius auratus gibelio. Its full length cDNA is 1091 bp and encodes a sequence of 147 amino acids, which shows 97.3% identity to zebrafish Mdkb on the amino acid level. RT-PCR analysis reveals that CagMdkb is first transcribed in gastrula embryos and maintains a relatively stable expression level during subsequent embryogenesis. Western blot analysis reveals a 19 kDa maternal CagMdkb protein band and the zygotic CagMdkb protein is expressed from gastrula stage. At around 10 somite stage, the 19 kDa CagMdkb is processed to another protein band of about 17 kDa, which might be the secreted form with the 21-residue signal peptide removed. With immunofluorescence analysis, maternal CagMdkb protein was found to be localized in each blastamere cell of early embryos. The zygotic CagMdkb positive fluorescence signal was detected from a pair of large neurons at 18-somite stage. At the later stages, CagMdkb protein was also extended to numerous small neurons in the forebrain, midbrain and hindbrain, as well as to nerve fibers in the spinal cord. Co-localization with 3A10 antibody revealed CagMdkb immunoreactivity on developing Mauthner neurons, a member of reticulospinal neurons. In addition, ectopic expression of CagMdkb in early embryos of gibel carp and zebrafish suppressed head formation and CagMdkb function was found to depend on secretory activity. All these findings indicate that CagMdkb plays an important role in neural development during gibel carp embryogenesis and there is functional conservation of Mdkb in fish head formation.

Distribution and bioaccumulation of microcystins in water columns: A systematic investigation into the environmental fate and the risks associated with microcystins in Meiliang Bay, Lake Taihu

For the purpose of understanding the environmental fate of microcystins (MCs) and the potential health risks caused by toxic cyanobacterial blooms in Lake Taihu, a systematic investigation was carried out from February 2005 to January 2006. The distribution of MCs in the water column, and toxin bioaccumulations in aquatic organisms were surveyed. The results suggested that Lake Taihu is heavily polluted during summer months by toxic cyanobacterial blooms (with a maximum biovolume of 6.7 x 10(8) cells/L) and MCs. The maximum concentration of cell-bound toxins was 1.81 mg/g (DW) and the dissolved MCs reached a maximum level of 6.69 mu g/L. Dissolved MCs were always found in the entire water column at all sampling sites throughout the year. Our results emphasized the need for tracking MCs not only in the entire water column but also at the interface between water and sediment. Seasonal changes of MC concentrations in four species of hydrophytes (Eichhornic crassipes, Potamogeton maackianus, Alternanthera philoxeroides and Myriophyllum spicatum) ranged from 129 to 1317, 147 to 1534, 169 to 3945 and 124 to 956 ng/g (DW), respectively. Toxin accumulations in four aquatic species (Carassius auratus auratu, Macrobrachium nipponensis, Bellamya aeruginosa and Cristaria plicata) were also analyzed. Maximum toxin concentrations in the edible organs and non-edible visceral organs ranged from 378 to 730 and 754 to 3629 ng/g (DW), respectively. Based on field studies in Lake Taihu, risk assessments were carried out, taking into account the WHO guidelines and the tolerable daily intake (TDI) for MCs. Our findings suggest that the third largest lake in China poses serious health threats when serving as a source of drinking water and for recreational use. In addition, it is likely to be unsafe to consume aquatic species harvested in Lake Taihu due to the high-concentrations of accumulated MCs. (C) 2007 Elsevier Ltd. All rights reserved.

Population dynamics and maturation cycle of Camallanus cotti (Nematoda : Camallanidae) in the Chinese hooksnout carp Opsariichthys bidens (Osteichthyes : Cyprinidae) from a reservoir in China

The seasonal population dynamics and maturation cycle of the nematode Camallanus cotti in the posterior intestine of Chinese hooksnout carp Opsariichthys bidens have been studied in the Danjiangkou Reservoir of the Hubei Province in central China from September 2004 to November, 2005. The overall prevalence, mean abundance and intensity of C cotti among fish sampled (n = 700 fish) were 47%, 2.29 +/- 12.38 ( +/- S.D.) and 1-307 (average 4.89 +/- 17.74), respectively. The overall sexual ratio of female to male nematodes (excluding L3 and L4 juveniles) was 1.17:1. Statistical results showed weakly positive correlations betweerl fish length and the number of nematodes per host. The dynamics of infection of the nematode exhibited significant seasonal pattern in changes in mean abundance. A similar pattern was found for changes in nematode prevalence, although this was not statistically significant. Higher levels of infection were observed among fish sampled in summer months and the lower in the winter. Neither the prevalence nor the abundance of the parasite was significantly different between male and female hosts. The pattern of frequency distribution of the parasite in the host was found to be over-dispersed throughout the sampling period. In addition, studies on the development and maturation of the parasite in O. bidens revealed that development (maturation), recruitment of the next generation, and reproduction may be continuous year-round, although reproduction may peak during the winter. (c) 2007 Elsevier B.V. All rights reserved.