cDNA cloning and characterization of a novel SNX gene differentially expressed in previtellogenic oocytes of gibel carp

To understand the molecular events governing fish oogenesis, a multiple technique was used to identify the genes differentially expressed at different phases during fish oogenesis. This technique is a combination of suppression subtractive hybridization, SMART cDNA synthesis and RACE-PCR. Here we report the cDNA cloning and expression characterization of a novel SNX gene based on its differential transcription between previtellogenic and fully mature oocytes in naturally gynogenetic gibel carp. First, a cDNA fragment selectively expressed in previtellogenic oocytes was identified and used to screen a SMART cDNA library prepared from the same mRNA sample by RACE-PCR for cloning fully length cDNA. The full length cDNA was 1392-bp long and coded for a novel SNX protein with 225 amino acids. The 5' UTR had 72 bp and 3' UTR had 642 bp. Unlike most of maternal genes that are transcribed after vitellogenesis and stored in oocytes, this gene is expressed at a higher level in the previtellogenic oocytes and at a much lower level in fully matured oocytes. However, RT-PCR analysis of tissues showed it was ubiquitous transcription. The novel gene is named fish sorting nexin (fSNX), because it contains a conserved PX domain. The fact which major expression of the gene occurs in the previtellogenic oocytes suggests that it might have an important function in the oogenesis. (C) 2003 Elsevier Inc. All rights reserved.

盘片式光纤传感器灵敏度计算方法

系统地开展了对各类盘片式光纤传感器灵敏度的研究工作。以周边固支、中心镶嵌刚性质量块的盘片式光纤加速度传感器为例，分析了传感器弹性盘片上各点的应力应变状态；结合迈克耳孙干涉仪原理，建立了计算传感器加速度灵敏度的数学模型，并讨论了粘贴光纤盘的最佳尺寸。制作两个相应的传感器进行对比实验，验证了上述计算模型的正确性。采用上述模型系统地推导了不同边界条件情况下盘片式光纤传感器的粘贴区域和灵敏度计算公式。对盘片式光纤传感器如光纤加速度传感器、光纤压力传感器、光纤水听器等的设计制作具有理论指导作用。

氨热法生长氮化镓晶体的数值模拟

氮化镓晶体是继单晶硅之后的一种新型的半导体材料. 本文利用有限体积法模拟了氨热法生长氮化镓晶体中流场的瞬态特性, 研究了隔板开孔10％时流场结构、温度场、浓度场. 发现对于隔板开孔率(10％)的情形, 中心开孔及边缘间隙的平均速度表现为振荡的特性, 中心开孔速度大多是正的, 边缘开孔大多是负的. 大的温度梯度发生在在高压釜壁面与液体的交界处与隔板周围. 物质由多孔介质区向生长区输运

利用力致分子动力学模拟方法构建剪切流场

<正>在传统计算力学的研究领域,利用Fluent等软件实现连续介质流体的模拟,已有很成熟的经验及范例;同时,分子动力学模拟也在其擅长的微观结构分析及预测领域有了长足的发展。但是到目前为止,连续介质力学仍无法和分子动力学方法有机地结合起来。因此,仍无法在分子动力学模拟体系构建理想的(即速度梯度和温度可控的)剪切流场。Grattona与Delgado-Buscalioni等的研究表明,在分子动力学模拟中,利用

多变量线性回归的平均值概念及其在地学研究中的应用

IEECAS SKLLQG

呼伦贝尔草原沙漠化现状、发展态势与成因分析

IEECAS SKLLQG

高能Ar~+辐照P型CdZnTe的电学特性和光致发光

采用能量 2 Ge V、剂量 10 1 0— 10 1 3cm- 2的 Ar+辐照 P型 Cd0 .96 Zn0 .0 4Te材料 ,对辐照前后和不同辐照剂量的样品进行了电学测试和光致发光研究 .实验结果和分析表明 ,Ar+ 辐照在 Cd0 .96 Zn0 .0 4Te中产生了更大密度的受主型缺陷和散射中心 ,引起材料载流子 (空穴 )浓度的增大和迁移率的降低 .随着辐照剂量的增大 ,载流子迁移率的降低要比载流子浓度增大得快 ,导致材料电阻随辐照剂量增大而增大

Study of nucleon resonances in a chiral quark model via eta productions

In this report we investigate eta-meson productions oil the proton via electromagnetic and hadron probes in a chiral quark model approach. The observables, such as, differential cross section and beam asymmetry for the two productions are calculated and compared with the experiment. The five known resonances S-11(1535) S-11(1650); P-13(1720) D-13(1520), and F-15(1680) are found to be dominant in the reaction mech-anisms in both channels. Significant, contribution from a new S-11 resonances are deduced. For the so-called "missing resonances", no evidence is found within the investigated reactions. The partial wave amplitudes for pi(-)p -> eta n are also presented.

文冠果的食用和药用价值

<正> 文冠果属无患子科文冠果属植物,别名文官果、文光果、木瓜等,是我国特有的一种优良木本食用油料树种。其适应性极强,根深、耐旱、耐寒、耐盐碱、耐脊薄,且综合价值高。分布于我国13个省(市、自治区)。1、文冠果的食用价值文冠果的果实含有高油脂及多种生物活性成分: