山羊骨髓间充质干细胞的分离培养

旨在对山羊的骨髓间充质干细胞(BMSCs)进行分离培养。将分离得到的BMSCs进行传代培养,采用RT-PCR法检测其干细胞转录因子oct4和sox2基因,以验证其干细胞特性;在此基础上绘制BMSCs的生长曲线,对其生物学特性进行直观了解。结果表明,分离到的山羊BMSCs原代细胞呈现出成纤维样,并能够表达oct4和sox2基因,证明了其干细胞特性;其生长曲线呈"S"型,在1~2 d时为潜伏期,第3天时进入指数生长期,第7天时进入平台期。结果提示,分离得到的细胞具有BMSCs的特性,能够用于后续的相关试验研究。     

Estimation of gillnet selectivity curve by maximum likelihood method

ABSTRACT: A maximum likelihood method of estimating gillnet selectivity when data are obtained by gillnet fleets consisting of several nets of differing mesh size is presented in this paper. The SELECT model is expanded by application of the relative length (i.e. the ratio of fish length to mesh size) to obtain a master curve of gillnet selectivity. Four kinds of functional model, normal, lognormal, skew-normal and bi-normal are fitted to the data. In addition, two cases in which the relative fishing intensity is either estimated or fixed by catch effort are compared. The bi-normal model has the lower model deviance regardless of whether the relative fishing intensity is estimated or not. The estimation of relative fishing intensity by catch effort is also examined in which the estimates of the parameter of the SELECT model are compared with the catch effort as determined by the number of nets of each mesh size used. For the bi-normal model these quantities compare well. Thus, it is concluded that this method gives reliable estimates even if data for each mesh size is obtained with different catch efforts.     

Fitting growth with the von Bertalanffy growth function: a comparison of three approaches of multivariate analysis of fish growth in aquaculture experiments

Three approaches for multivariate analysis of fish growth in aquaculture experiments with Nile tilapia (Oreochromis niloticus niloticus L.) based on the von Bertalanffy growth curve are presented and compared. The approaches are: an extended Gulland‐and‐Holt (GH) plot, a forced extended GH plot and a multilinear regression analysis for the growth parameter K. All three models provide valuable insight into the major environmental factors influencing the daily growth rate and explain 28–46% of the variance of the observed daily growth rate of the used data set. For all three methods, the modelled parameter is significantly related to the net yield of Nile tilapia and can, therefore, be used for the predictive modelling of management scenarios. The extended GH plot loads the influence of environmental parameters upon L_∞, while the forced extended GH plot and Direct fitting of K load the influence on the growth parameter K. The latter is more in the tradition of aquaculture research. But the forced extended GH plot and Direct fitting of K can only be applied if L_∞ of the cultured species is known, as the selected L_∞ influences the variance in the regression variables.     

低温寡照条件下黄瓜叶片光合作用减弱的机理分析

以黄瓜品种‘津优101’（Jinyou101）为试材,于2020−2021年在南京信息工程大学利用人工气候箱开展低温寡照双因素环境控制试验。昼/夜温设置13℃/3℃、16℃/6℃、19℃/9℃、22℃/12℃共4个水平,光合有效辐射（PAR）设置200和400μmol·m−2·s−1两个水平,各处理均分别持续3、6、9、12d,以28℃/18℃和800μmol·m−2·s−1的光温设置为对照（CK）。测定不同处理下幼苗期黄瓜叶片的叶绿体色素含量、光合参数和快速叶绿素荧光诱导动力学参数,以探究低温寡照条件下黄瓜幼苗叶片光合作用减弱的机理。结果表明：（1）不同处理下黄瓜叶片的各叶绿体色素含量均随温度和PAR降低而降低,随处理时间延长而降低。（2）不同处理下叶片最大光合速率（Pmax）、光饱和点（LSP）、气孔导度（Gs）和蒸腾速率（Tr）均随胁迫程度和时间的增加呈降低趋势,光补偿点（LCP）随胁迫程度和时间的增加呈上升趋势,说明低温寡照胁迫程度越深、胁迫时间越长,黄瓜叶片光合作用越弱。（3）随着胁迫程度加深和时间延长,黄瓜叶片快速荧光诱导动力学曲线（OJIP曲线）的JIP相逐渐下降;能量分配比率参数（φPo、ψEo和φEo）均逐渐减小;单位活性反应中心所吸收（ABS/RC）和捕获（TRo/RC）的光能逐渐增加,但用于电子传递的光能（ETo/RC）仍逐渐减少。本研究证实,低温寡照处理使黄瓜叶片气孔导度下降,气体交换受阻;天线色素含量降低,叶片吸收和捕获的光能减少;PSII性能降低,用于光化学反应的能量减少,因而叶片光合作用减弱。     

四级轴流透平的性能研究

以汉诺威大学四级轴流实验涡轮为对象,利用当今先进的流体数值模拟软件NUMECA对其不同工况下的内部流场进行了数值模拟,获取同一工况下流场损失分布特点,从而为透平的优化提供理论基础。通过改变涡轮出口背压的方法,画出不同工况下该四级轴流透平的特性曲线,并在特性曲线上获得效率最高点、流量最大值点、流量最小值点。并通过对比获得最大效率点处不同级透平的流场损失分布。利用相同的方法分析同一工况或不同工况下整个四级透平的流场的损失分布。     

土壤水分特征曲线自动检测系统的设计与应用

[目的]为了更好地满足现代农业各种种植环境下作物对水分要求越来越精准,结合土壤含水量与土壤水分势能的概念,设计了土壤水分特征曲线自动检测系统。[方法]利用电子式土壤水分张力传感器实时测定供试盆钵中土壤水分的张力数值,同时采用电子式重量传感器测定土壤重量,利用差减法计算土壤含水量,并绘制土壤水分特征曲线。[结果]通过对江苏地区2种不同质地土壤实地测定得出：质地不同水分特征曲线走势不同,分别为：徐州地区黄河古道砂质土水分特征曲线关系式为 Y=-0.0002X3＋0.0277X2-1.6445X＋38.161,R2=0.9919;大丰金海农场盐碱土水分特征曲线关系式为 Y=-0.002X2-0.426X＋39.905,R2=0.9913。[结论]土壤水分特征曲线自动检测系统可以同时反应土壤含水量和土壤水分势能状况,可反映土壤水分对植物生长的有效性,为科学灌溉提供依据。     

棕壤土水分特征曲线拟合的比较分析

以棕壤土为对象,采用压力膜法测定均质原状土壤样品一系列含水率和对应基质势值,分别用幂函数和Van Genuchten （1980）模型进行拟合,并与实测含水率数据进行比较。结果表明：压力膜法测定土壤水分特征曲线是可行的,所得试验结果合理,可用于土壤水分动态模拟。     

Milk Yield of Holstein Cows Induced into Lactation Twice Consecutively and Lactation Curve Models Fitted to Artiifcial Lactations

Nineteen multiparous barren Holstein cows were subjected to an induction of lactation protocol for 21 d administering estradiol cypionate （2 mg kg-1 of body weight （BW） d-1, on day 1 to 14）, progesterone （0.10 mg kg-1 of BW, on day 1 to 7）, lfumethasone （0.03 mg kg-1 of BW, on day 18 to 20） and recombinant bovine somatotropin （rbST;500 mg per cow, on day 1, 6, 16 and 21）. At the end of lactation and with a minimum of a 2-mon dry period, the same cows were again hormonally induced into lactation. Cows in both lactations were not artiifcially inseminated, they were milked 3 times daily and received rbST throughout lactation. Mean accumulated milk yield at 305 d in milk （DIM） did not differ between the ifrst and second induced lactations （（9 710 ＆#177;1 728） vs. （9 309＆#177;2 150） kg;mean＆#177;SD）. Total milk yield （（12 707＆#177;3 406） vs. （12 306＆#177;4 218） kg;mean＆#177;SD） and lactation length （（405＆#177;100） vs. （410＆#177;91） d;mean＆#177;SD） were not different between the ifrst and second induced lactations. In a second study, 15 empirical models including exponential, power law, yield-density, sigmoidal and miscellaneous models were compared for their suitability by modeling 12-mon （n=334）, 18-mon （n=164） and 29-mon （n=22） lactation cycles of Holsteins cows induced into lactation and treated with rbST throughout the lactation. Hoerl （Y=ab1/xxc）, Wood （Y=axb exp（cx）） and Dhanoa （Y=ax（bc）exp（cx）） models were equally suitable to describe 12-mon lactations. An exponential model with ifve parameters （Y=exp（a＋bx＋cd2＋e/x）） showed the best ift for milk yield for 18-mon lactations. The rational model （Y=a＋bx/1＋cx＋dx2） was found to produce the closest ift for 29-mon lactations. It was concluded that, with the protocol used in the present study, multiparous cows respond favorably to a second cycle of induced lactation, with milk yield similar to that experienced during the ifrst cycle. Thus, dairy producers might be able to lengthen the productive life of infertile high producing cows with a renewal of artiifcial lactation, which would imply an overall reduction in voluntary culling of cows. Also, various equations used to describe the lactation curves demonstrated the potential for iftting monthly milk records of Holstein cows with prolonged lactations and induced hormonally into lactation.     

特殊园林道路平曲线施工放线新方法

园林道路平曲线的施工放线是一项比较繁难的工作.当园林绿地中的园路紧靠建筑物、水体等特殊环境,园路平曲线的交点和圆心都被遮挡或无法定位时,常规的园路平曲线放线方法有的不适用,有的则太复杂.针对这种特殊园路平曲线的放线工作情况,根据在工作中的探索,介绍了一种新颖的、简便的园路平曲线施工放线方法,并对此方法的操作步骤和适用范围及注意事项进行了详细的说明,旨在利用简单的工具准确高效地完成施工放线工作.     

青海贵德地区潜水含水层弥散系数研究

以青海贵德地区作为研究区域,以NaCl作为示踪剂,一次性瞬时投放,进行野外弥散试验,观测示踪剂浓度随时间的变化过程,使用标准曲线配线法和使用Matlab数据拟合法进行求解,得到了责德地区潜水含水层弥散系数,并分析了试验结果,比较了两种计算方法.