脂肪酸钙对放牧肉牛超数排卵效果及雌二醇和孕酮水平的影响

以探讨添加脂肪酸钙对放牧肉牛(婆罗门和BMY)超数排卵效果及血中雌二醇(E2)和孕酮(P4)水平的影响为目的.将48头供体分为Ⅰ(放牧或对照组)、Ⅱ(放牧+浓缩饲料500 g/d)和Ⅲ(放牧+浓缩饲料500 g/d+脂肪酸钙100 g/d)3组,从同期发情处理开始到冲胚结束试验期32 d,并对供体牛在8个处理时段进行采血,用放射免疫分析法(RIA)分析E2和P4水平.试验结果表明:Ⅰ,Ⅱ,Ⅲ组供体牛超数排卵的排卵率分别为75.4%,74.4%和81.7%(P＞0.05),受精率分别为81.4%,55.6%和93.2%(P＞0.05);获胚(卵)数分别为7.0枚,6.3枚和7.3枚(P＞0.05),可用胚数分别为3.9枚,2.6枚和4.7枚,Ⅲ组显著高于Ⅱ组(P＜0.05);E2平均水平分别为0.57 pg/mL,0.47 pg/mL和0.63 pg/mL(P＞0.05),P4平均水平分别为3.53 ng/mL,5.03 ng/mL和3.74 ng/mL,Ⅱ组高于Ⅰ,Ⅲ组(P＜0.01).表明适量添加脂肪酸钙能改善全放牧肉牛的营养、增强体质,促进排卵与受精,增加超数排卵的可用胚数;能使供体牛的E2和P4水平比对照组有所提高;添加效果冬、春季优于夏、秋季.

Stable RNA hairpins in 88 coding regions of human mRNA

RNA hairpins containing UNCG, GNRA, CUUG (N = A, U, C or G, R = G or A) loops are unusually thermodynamic stable and conserved structures. The structural features of these hairpin loops are very special, and they play very important roles in vivo. They are prevalent in rRNA, catalytic RNA and non-coding mRNA. However, the 5' C(UUCG)G 3' hairpin is not found in the folding structure of 88 human mRNA coding regions. It is also different from rRNA in that there is no preference for certain sequences among tetraloops in these 88 mRNA folding structures.

保安湖大型底栖动物结构与分布格局研究

2001年8月对保安湖大型底栖动物进行调查,共记录动物4门7纲25科54属70种。其中,软体动物为绝对优势类群(占总丰度的81.5%)。而腹足类的纹沼螺(Parafossarulus striatulus)、白旋螺(Gyraulus albus)、长角涵螺(Alocinma longicornis)、方格短沟蜷(Semisulcospira libertina)和铜锈环棱螺(Bellamya aeruginosa)为该湖泊的优势种。样点间平均物种丰富度7.1,平均Shannon-Winner指数1.34。

斜带石斑鱼囊胚期胚胎和尾芽期胚胎差异表达基因的筛选及克隆

以斜带石斑鱼囊胚期胚胎和尾芽期胚胎分别作为检验组和驱动组,构建了石斑鱼囊胚期胚胎和尾芽期胚胎的抑制性差减杂交cDNA文库。以α-tubulin作为检测指标,显示差减效率分别高达28和27。分别取囊胚期胚胎和尾芽期胚胎各192和960个PCR阳性克隆进行斑点杂交,得到15个囊胚期和131个尾芽期的斑点杂交阳性克隆。测序和数据库比对分析表明,囊胚期15个阳性克隆中有11个已知基因的cDNA片段和没有同源性的4个cDNA片段;而在尾芽期的131个阳性克隆中,有123个已知基因的cDNA片段和8个没有同源性的cD

水生大型无脊椎动物的能量密度

测定了 72种大型水生无脊椎动物的能量密度 ,其中 6 9种是第一次测定 .底栖动物的能量密度随物种、季节、地区、年龄等的不同而存在差异 .绝大多数寡毛类的能量密度为 2 2 .99- 2 5 .0 8kJ/g(干重 ) ,软体动物的能量密度为 16 .72 - 2 2 .99kJ/g(干重 ) ,昆虫及其幼虫的能量密度变异较大 ,为 10 .4 5 - 2 5 .0 8kJ/g(干重 )左右 .

保安湖麦穗鱼种群生物学V.生产力

在 1 995年 1 0月至 1 996年 1 1月 ,依据有关种群参数估算了保安湖 1 # 试验围拦中麦穗鱼的生产力。月平均瞬时生长率的变化与年龄和季节有关 ,随着年龄增加生长率降低 ,在生活史的早期阶段生长最快 ,生长率一般在春、夏季较高。在研究期间 ,种群平均生物量为1 8 2 7kg·hm- 2 ,周年生产力为 36 53kg·hm- 2 ·a- 1 ,P/B系数为 2 0。 1 996世代对总生产力的贡献为 67 9%。种群月平均生物量及生产力均表现出了较明显的季节变化 ,生物量在秋季(9月 )

Nonlinear phenomena in thermoacoustics: A comparison between single-mode and multi-mode methods

Nonlinear analysis of thermoacoustic instability is essential for prediction of frequencies and amplitudes of limit cycles. In frequency domain analyses, a quasi-linear transfer function between acoustic velocity and heat release rate perturbations, called the flame describing function (FDF), is obtained from a flame model or experiments. The FDF is a function of the frequency and amplitude of velocity perturbations but only contains the heat release response at the forcing frequency. While the gain and phase of the FDF provide insight into the nonlinear dynamics of the system, the accuracy of its predictions remains to be verified for different types of nonlinearity. In time domain analyses, the governing equations of the fully coupled problem are solved to find the time evolution of the system. One method is to discretize the governing equations using a suitable basis, such as the natural acoustic modes of the system. The number of modes used in the discretization alters the accuracy of the solution. In our previous work we have shown that predictions using the FDF are almost exactly the same as those obtained from the time-domain using only one mode for the discretization. We call this the single-mode method. In this paper we compare results from the single-mode and multi-mode methods, applied to a thermoacoustic system of a premixed flame in a tube. For some cases, the results differ greatly in both amplitude as well as frequency content. This study shows that the contribution from higher and subharmonics to the nonlinear dynamics can be significant and must be considered for an accurate and comprehensive analysis of thermoacoustic systems. Hence multi-mode simulations are necessary, and the single-mode method or the FDF may be insufficient to capture some of the complex nonlinear behaviour in fhermoacoustics.

中华鲟(Acipenser sinensis)及相关种类的mtDNA控制区串联重复序列及其进化意义

采用 PCR技术和 DNA测序技术 ,发现了我国一级珍稀保护动物中华鲟 ( Acipensersinensis)线粒体 DNA( mt DNA)的控制区 ( D- loop)存在数目不等的串联重复序列 ,该重复序列造成了中华鲟广泛的异质性现象 .从分子水平进行了不同类型重复序列变化规律的研究 ,同时还初探了重复序列在我国其它几种鲟鱼类的存在情况 ,发现在白鲟 ( Psephurus gladius)、达氏鲟 ( A.dabryanus)和史氏鲟 ( A.schrenckii)均存在类似的重复序列结构 .序

人工湿地生态系统的除藻研究

国家杰出青年科学基金(3992 50 0 7); 欧盟国际合作项目(ERBIC 1 8CT 960 0 59)

利用EIA生物测试法快速定量筛选环境样品中的二噁污染物

将采集的环境样品分作 3份 ,1份用于高分辨色质联用多离子检测测定二的毒性当量浓度 TEQ,另 2份分别用 7-乙氧基 -异吩唑酮 -脱乙基酶 ( EROD)活力诱导法和酶免疫法 ( Enzyme Immuno Assay,EIA)进行生物测试 .结果表明 EIA和EROD这 2种生物试验方法均具有较好的准确性和很宽的线性范围 .比较 Micro- EROD分析结果与化学分析结果以及 EIA分析结果与化学分析结果 ,发现 Micro- EROD生物试验所测得的 TEQ值均高于化学分析法的 TEQ值

氯化高汞对大型溞的慢性毒性

在换水静置条件下(25℃),氯化高汞(以Hg~(++)计)对大型溞的48小时LC_(50)值及其可信限为13.5(±2.1)微克/升。试验个体饲以斜生栅藻单个培养,在汞含量为1—21微克/升浓度下,产仔总数经方差分析表明组间差异显著(F>F_(0.05))。各浓度组(X)与产仔总数(Y)的关系为:Y=-51.823X+4320.960(r=-0.904,p<0.01)。净增殖率(R_0)随浓度升高而逐渐下降。存活和生长用方差分析及D值检验表明对照组与各浓度组之间(差异数分别小于各自的D值20.89和0.1

Effect of dietary cyanobacteria on growth and accumulation of microcystins in Nile tilapia (Oreochromis niloticus)

A 12-week growth trial was conducted in a flow-through system to investigate the chronic toxic effect of dietary intake of cyanobacteria on growth, feed utilization and microcystins accumulation in Nile tilapia (Oreochromis niloticus L.) (initial body weight: 5.6 g). Six isonitrogenous and isocaloric diets were formulated to include different contents of cyanobacteria with the dietary microcystins increasing from 0 to 5460.06 ng/g diet. The results showed that dietary intake of cyanobacteria could increase the growth of tilapia while there are no impacts on feed conversion efficiency or mortality. Feeding rate was higher for the diets containing highest cyanobacteria. Microcystins were mostly accumulated in fish liver. The relationship between microcystins contents in muscle, liver, spleen and dietary intake could be described by quadratic equations. Microcystins content in the muscle of Nile tilapia in present study exceeded the upper limit of the tolerable daily intake (TDI) of microcystins suggested by the WHO (0.04 mu g/kg body weight/d). It is suggested that Nile tilapia fed on toxic cyanobacteria is not suitable for human food. (c) 2006 Elsevier B.V. All rights reserved.

Computational modelling of building damage due to tunnelling

Underground constructions in soft ground may lead to settlement damage to existing buildings. In The Netherlands the situation is particularly complex, because of the combination of soft soil, fragile pile foundations and brittle, unreinforced masonry façades. The tunnelling design process in urban areas requires a reliable risk damage assessment. In the engineering practice the current preliminary damage assessment is based on the limiting tensile strain method (LTSM). Essentially this is an uncoupled analysis, in which the building is modelled as an elastic beam subject to imposed Greenfield settlements and the induced tensile strains are compared with a limit value for the material. The soil-structure interaction is included only as a ratio between the soil and the building stiffness. In this paper, a coupled approach is evaluated. The soil-structure interaction in terms of normal and shear behaviour is represented by interface elements and a cracking model for masonry is included. This project aims to improve the existing damage classification system for masonry buildings subjected to tunnel-induced settlement, in order to evaluate the necessity of strengthening techniques or mitigation measures.

Study of GaN thin films grown on vicinal SiC (0001) substrates by molecular beam epitaxy

A detailed study of the characteristics of undoped GaN films, grown on either vicinal or nominal flat SiC (0001) substrates by molecular beam epitaxy, has been carried out using photoluminescence and Raman scattering techniques. The I I K photoluminescence spectra of the GaN film grown on the vicinal SiC (0001) substrate show a strong and sharp near-bandgap peak (full width at half maximum (FWHM) similar to 16 meV). This feature contrasts with that of the GaN film grown on the nominal flat SiC (0001) substrate where the I I K photoluminescence spectra exhibit the near-bandgap peak (FWHM similar to 25 meV) and the intensity is approximately seven times weaker than that of the vicinal film sample. The redshift of the near-bandgap peak associated with excitons bound to shallow donors is related to the stress caused by both the lattice mismatch and the thermal expansion coefficient difference between GaN and SiC substrates. The measured thermal activation energy of the shallow donor of 33.4 meV is determined by using an Arrhenius plot of the near-bandgap luminescence versus I IT from the slope of the graph at high temperature. The temperature dependence of the FWHM of the near-bandgap luminescence has also been studied. The Raman scattering measurements from the vicinal film reveal that the E-2 phonon peak is strengthened and the A(1)(LO) phonon peak is shifted towards the low-frequency side with enhanced intensity, in comparison to that from the nominal flat film, suggesting a reduction in the density of defects and a lower free carrier concentration in the vicinal GaN film.