Increasing the genetic uniformity of bighead carp [Aristichthys nobilis (Richardson)] by means of spontaneous diploidization of gynogenetically activated eggs

Three groups of gynogenetic diploid bighead carp were successfully obtained by means of artificial gynogenesis. The activation rates of gynogenesis varied from 75.9% to 98.8%, and the frequency of spontaneous diploidization was around 0.4%. Over 2000 normally gynogenetic diploid fry were obtained in three gynogenetic groups. The haploid karyotype consisted of nine metacentric, 12 submetacentric, three subtelocentric chromosomes and 45 arms. The chromosome number was 48 from gynogenetic diploid. The results showed that the genetic material of offspring was maternal. The aneuploid hybrid embryos of bighead carp and Xingguo red common carp with chromosome numbers ranging from 28 to 73 did not survive post hatch, likely the result of incompatibility between the nucleus and the cytoplasm of two parents. Sixty RAPD primers from three groups were used for total DNA amplification of gynogenetic offspring, maternal and 'paternal' fish. A total of 451 bands were amplified from three kinds of samples above. From maternal bighead carp, 256 bands were amplified; however, there were 251 shared bands between maternal and gynogenetic bighead carp. From artificial gynogenetic offspring, two 'paternal' DNA segments without an expression function were found. An UPGMA tree showed that gynogenetic offspring were closely clustered and the genetic identity among them was very high (0.956).

Isolation and characterization of six microsatellite markers in the large yellow croaker (Pseudosciaena crocea Richardson)

Six polymorphic microsatellite markers were isolated and characterized using an enriched library technique in the large yellow croaker (Pseudosciaena crocea Richardson, 1864), a commercially important marine fish in China. They showed PIC (polymorphism information content) ranging from 0.064 to 0.885 (average of 0.580) and allele numbers ranging from two to 13 (average of 7.5), which were useful for the studies on population genetics and selective breeding of the large yellow croaker.

Induction of triploidy in large yellow crocker Pseudosciaena crocea (Richardson, 1846): effects of pressure shocks and growth performance in the first rearing year

The precociously sexual maturation in large yellow crocker Pseudosciaena crocea has become a serious problem. In an attempt to solve this problem, the production of sterile triploids could be an effective strategy. In this study, triploid P. crocea was obtained by subjecting fertilized eggs to pressure shock. Flow-cytometry analysis was used to assess ploidy level. In terms of triploid rate and hatching rate, the optimal conditions of pressure shock for triploidy induction in P. crocea were 7500 psi for 3 min shock at 3 min after fertilization at 20 degrees C. With the application of these parameters, 100% triploid fish were produced. During the first rearing year, triploid P. crocea had a similar growth performance compared with its diploid counterpart before the age of 8 months and showed a significant advantage at the age of 10 and 12 months in body weight and body length (P < 0.05). At the age of 12 months, the carcass weight of triploids was markedly higher than that of diploid control, and gonadal somatic index was significantly lower than that of their diploid control. During the first rearing year, survival in triploid group was 76.44%, inferior to its diploid control (83.21%).

液–固脉冲流化床中浓度波传播与衰减

采用数值计算和实验验证相结合的方法研究液一固脉冲流化床中浓度波的传播和衰减。当脉仲开半周期乃和闭半周期乃都远大于颗粒弛豫时间吊时,两相的惯性力之差在一个周期的绝大部分时间中相对于重力很小,可忽略,这时由双流体模型的动量方程可推导出推广的Richardson-Zaki公式,双流体模型简化为局部平衡模型。采用五阶精度WENO格式求解浓度波传播方程,得到了脉冲流化过程中浓度波传播与衰减的规律,与实验结果符合良好。

Dynamics Of Fine Particles In Liquid-Solid Fluidized Beds

On the basis of the Local Equilibrium Model (LEM), fine particles with large Richardson-Zaki exponent n show, under certain conditions during bed expansion and collapse, different dynamic behavior from particles with small n. For an expansion process there may be a concentration discontinuity propagating upward from the distributor, and, on the contrary, for a collapse process there may be a progressively broadening and upward-propagating continuous transition zone instead of discontinuity. The predictions of the bed height variation and the discontinuity trace have been validated experimentally. (c) 2007 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Novel experimental phenomena of fine-particle fluidized beds

The dynamic response of bed height and concentration waves in liquid-solid fluidized beds to a step change in the fluidization velocity is considered. We experimentally study the liquid-solid fluidized beds, spherical beadings, with sizes ranging from 230 to 270 mesh and the inner diameter of columns made from glass is 2.4 mm. Experimental results find that under certain conditions, fine particles with large Richardson-Zaki exponent n display different dynamic behavior from usual particles with smaller n during expansion and collapse of the fluidized state. (c) 2007 Elsevier Inc. All rights reserved.

双螺旋尾涡结构和内波实验研究

密度分层流体中物体统流的实验研究从六十年代中期起蓬勃开展起来。在1967年Mowbray和Rarity发表了三张纹影照片,但是没有涉及到尾涡结构。在这期间,不少学者研究了水平运动产生的内波,到了1977年Pao和Kao首先报导了用弱分层的方法揭示了在小Richardson数R_i=0.215和雷诺数Re=4×10~3～2×10~4情况下在均匀流中圆球的尾涡具有封闭末端双螺旋结构。Merzkirch和他的学生用光学技术得到清晰的内波波型照片,对圆柱垂直运动实验和理论结果作了比较。近些年来,稳定性研究和三维分离流动中流面分叉及涡构架研究有新进展。为了搞清楚密度分层流体中的尾涡结构、内波和尾涡的关系、内波产生的机理,在1983年我们建立了分层流水箱设备。从实验中我们发现:在低雷诺数Re≈10~2情况下,分层流体中圆柱绕流的尾涡具有双螺旋结构,双螺旋的二支以相反的方向连续地缠绕在一起。这与Pao和Kao水平运动圆球尾流中涡结构有类似的现象。在有倾角情况下,涡管在运动中发生变形。可以认为,实验结果有助于剪切流动现象的研究以及对湍流的发生、发展和衰变机制的进一步理解。 本实验使用直径D=20mm,长度70mm的不锈钢圆柱模型,该模型水平地悬挂在分层流水箱框架中的带有滚珠轴承滑块上。圆柱与水平轴成45°和90°倾角向上和向下被拖着

Potential energy model for turbulent entrainment across density interface in a linearly stratified fluid

A potential energy model is developed for turbulent entrainment in the absence of mean shear in a linearly stratified fluid. The relation between the entrainment distance D and the time t and the relation between dimensionless entrainment rate E and the local Richardson number are obtained. An experiment is made for examination. The experimental results are in good agreement with the model, in which the dimensionless entrainment distance D is given by DBAR = A(i)(SBAR)-1/4(fBAR)1/2(tBAR)1/8, where A(i) is the proportional coefficient, S is the dimensionless stroke, fBAR is the dimensionless frequency of the grid oscillation, tBAR the dimensionless time.

Growth of zero-mean-shear turbulent-mixed layer with suspended particles in a 2-layer fluid system

The growth behaviour of zero-mean-shear turbulent-mixed layer containing suspended solid particles has been studied experimentally and analysed theoretically in a two-layer fluid system. The potential model for estimating the turbulent entrainment rate of the mixed layer has also been suggested, including the results of the turbulent entrainment for pure two-layer fluid. The experimental results show that the entrainment behaviour of a mixed layer with the suspended particles is well described by the model. The relationship between the entrainment distance and the time, and the variation of the dimensionless entrainment rate E with the local Richardson number Ri1 for the suspended particles differ from that for the pure two-layer fluid by the factors-eta-1/5 and eta-1, respectively, where eta = 1 + sigma-0-DELTA-rho/DELTA-rho-0.

A Simple Model For Predicting The Void Fraction Of Gas/Non-Newtonian Fluid Intermittent Flows In Upward Inclined Pipes

In this work, a simple correlation, which incorporates the mixture velocity, drift velocity, and the correction factor of Farooqi and Richardson, was proposed to predict the void fraction of gas/non-Newtonian intermittent flow in upward inclined pipes. The correlation was based on 352 data points covering a wide range of flow rates for different CMC solutions at diverse angles. A good agreement was obtained between the predicted and experimental results. These results substantiated the general validity of the model presented for gas/non-Newtonian two-phase intermittent flows.

Investigation on average void fraction for air/non-Newtonian power-law fluids two-phase flow in downward inclined pipes

The present work has been carried out to investigate on the average void fraction of gas/non-Newtonian fluids flow in downward inclined pipes. The influences of pipe inclination angle on the average void fraction were studied experimentally. A simple correlation, which incorporated the method of Vlachos et al. for gas/Newtonain fluid horizontal flow, the correction factor of Farooqi and Richardson and the pipe inclination angle, was proposed to predict the average void fraction of gas/non-Newtonian power-law stratified flow in downward inclined pipes. The correlation was based on 470 data points covering a wide range of flow rates for different systems at diverse angles. A good agreement was obtained between theory and data and the fitting results could describe the majority of the experimental data within ±20%.

Natural selection on EPAS1 (HIF2 alpha) associated with low hemoglobin concentration in Tibetan highlanders

By impairing both function and survival, the severe reduction in oxygen availability associated with high-altitude environments is likely to act as an agent of natural selection. We used genomic and candidate gene approaches to search for evidence of such genetic selection. First, a genome-wide allelic differentiation scan (GWADS) comparing indigenous highlanders of the Tibetan Plateau (3,200 3,500 m) with closely related lowland Han revealed a genome-wide significant divergence across eight SNPs located near EPAS1. This gene encodes the transcription factor HIF2 alpha, which stimulates production of red blood cells and thus increases the concentration of hemoglobin in blood. Second, in a separate cohort of Tibetans residing at 4,200 m, we identified 31 EPAS1 SNPs in high linkage disequilibrium that correlated significantly with hemoglobin concentration. The sex-adjusted hemoglobin concentration was, on average, 0.8 g/dL lower in the major allele homozygotes compared with the heterozygotes. These findings were replicated in a third cohort of Tibetans residing at 4,300 m. The alleles associating with lower hemoglobin concentrations were correlated with the signal from the GWADS study and were observed at greatly elevated frequencies in the Tibetan cohorts compared with the Han. High hemoglobin concentrations are a cardinal feature of chronic mountain sickness offering one plausible mechanism for selection. Alternatively, as EPAS1 is pleiotropic in its effects, selection may have operated on some other aspect of the phenotype. Whichever of these explanations is correct, the evidence for genetic selection at the EPAS1 locus from the GWADS study is supported by the replicated studies associating function with the allelic variants.

黄颡鱼鳃部寄生单殖吸虫和鳋类的空间分布特点

研究了黄颡鱼Pelteobagrusfulvidraco (Richardson)鳃部的寄生单殖吸虫 (Monogeneans)和鳋类 (Copepods)的空间分布特点。寄生于黄颡鱼鳃部的单殖吸虫和鳋类在两侧鳃上的感染强度及其差异表明 ,两种寄生虫对于鳃片的左右位置没有明显的选择性 ;在黄颡鱼四鳃间的分布存在极显著的差异 (P <0 .0 5 ,P <0 .0 1) ;在鳃片的各区均存在选择性 ;对鳃丝的各分段也均有极显著的选择性。