卵泡刺激素受体基因作为产仔数候选基因的研究

分析了FSHR基因2个位点（FSHRA、FSHRB）的PCR－SSCP、PCR－RFLPs多态性，利用SAS软件分析了多态性与母猪产仔数间连锁关系。找到了1个影响产仔数的新的变异位点FSHRB，该位点多态性显著地影响猪产仔数性状，即基因型BB的产仔数显著地高于AB、AA基因型。结果显示出该位点具有作为常规选育的辅助选择的有效的分子标记潜力。     

Interspecific differences in early life‐history traits in a species complex of stream‐resident galaxiids

Fish differentially provision resources to eggs and larvae to optimise survival during the critical early life‐history period. Resource allocation is limited by a trade‐off between egg size and fecundity, and the optimal strategy varies with habitat type. This study examines the consequences of egg size differences for the early life‐histories of four closely related galaxiid species which occur in contrasting habitat types on the South Island, New Zealand. Headwater species had substantially larger water‐hardened eggs, longer incubation times, and newly hatched larvae were on average up to 41% longer than lower catchment species. Significant interspecific differences in gape diameter, eye diameter and myomere depth were also observed. Swimming ability was positively associated with larval length at hatch. Interspecific differences in length and swimming ability were generally maintained throughout the larval period, despite larvae being reared under relatively benign conditions where many other studies suggest initial differences should disappear. These results demonstrate the consequences of differential maternal provisioning to the egg for larval traits. The larger larvae of headwater species are likely to be more resistant to starvation and have improved foraging ability compared to lower catchment species; traits which are likely to confer them survival advantages in the low productivity, food‐scarce environments they occupy. The smaller larvae of lower catchment species are likely to be a consequence of females investing in fecundity in these relatively resource‐rich streams.     

Census and effective population sizes of white‐spotted charr (Salvelinus leucomaenis) in a fragmented landscape

Several habitat models have been proposed to predict population size for stream fishes and to guide habitat assessment and monitoring techniques. However, most models do not incorporate the potential advantage of molecular genetic markers. We conducted a field survey and microsatellite DNA analyses to quantify the relationships among genetic diversity, census/effective population size and habitat variables in fragmented populations of white‐spotted charr (Salvelinus leucomaenis). The census population size significantly increased with the stream length, the number of pools and a pool‐riffle sequence index, a proxy for channel‐unit habitat type complexity within reaches. Population density was correlated with the pool‐riffle sequence index only. Genetic diversity and effective population size were not correlated with the habitat variables or census population size. There was a lack of isolation‐by‐distance population structure in the studied populations. Our results suggest that stream length and the number of pools within reaches associated with habitat complexity are the habitat variables that explain the majority of variation in population size of white‐spotted charr. Our findings provide further evidence that census population size per se is a poor indicator of the inclusive genetic diversity within populations in a fragmented landscape.     

Investigation of the Effect of Mesh Size on the Effectiveness of Hotplate Aqua Regia Extractions

Aqua regia extractions with subsequent inductively coupled plasma determinations are a very common method of elemental analysis of soils and sediments. Before extraction, the material must be dried and sieved. Small variations in this early step can have a significant impact on the later outcomes, especially for unassisted (for example, without ultrasonic or microwave) extraction procedures. Therefore the impact of mesh size on the sieving process was investigated. A mesh size of 2.0 mm or greater yielded unacceptably high variations between the subsamples and a very poor recovery rate when compared to a 0.063-mm sieve. A mesh size of 0.3 mm resulted in the best outcomes, losing nearly no material in the fine sediment samples and about a tenth in the coarse samples. The precision was high for the 0.3-mm samples as well, only negligibly surpassed by the 0.1-mm samples for some materials.     

农业机械手钳的人机安全设计

分析了应用较为普遍的农业机械工具—农业手钳的人机安全学设计因素,并通过实验计算得出以人机工程学为基础的手钳的参数设计。主要从人机工程学的角度出发,通过分析手钳在使用时的舒适度和把手尺寸,以评估设计的合理性。同时,分别针对男女群体正态分布的第5百分位、第5 0百分位和第9 5百分位的测量数据进行手柄设计和尺寸评估,得出农业机械手钳的科学合理性尺寸设计。     

基于最小二乘法的落叶松木粉粒径数学建模与分析

【目的】建立落叶松木粉粒径与长宽比的数学模型，通过分析数学模型和其二阶导数，揭示木粉长宽比随粒径减小的变化趋势及变化的根本原因，获得最大长宽比对应的粒径，为建立长宽比与力学性能之间的定量关系提供参考。【方法】利用光学显微镜拍摄获得木粉的显微图像，测算获得目标木粉成熟管胞的平均长度、平均宽度以及木粉粒径的大小。通过数字图像处理技术提取单木粉颗粒的矩形度、长宽比：将原始木粉显微图像由 RGB颜色空间转到Lab颜色空间，提取其b分量；对b分量图像用3×3模板进行中值滤波；用K-means算法将去噪后图像聚类为2类，得木粉的二值图像；对二值图像用5×5的结构元素进行先开启后闭合的数学形态学运算；用八连通区域法标记图像中的单木粉颗粒；对标记后图像用目标区域像素点个数统计法计算获得单木粉颗粒的几何面积，用主轴法获得单木粉颗粒的最小外接矩形的长、宽、面积；计算获得单木粉颗粒的长宽比、矩形度数据。采用最小二乘法对木粉粒径与长宽比进行数据拟合，通过分析评判多项式、高斯和傅里叶3种拟合函数后选用高斯方程表达得木粉粒径与木粉长宽比的数学模型，再根据其拟合曲线方程计算得其二阶导数，结合模型的二阶导数和测算得的木粉管胞数据对高斯模型进行分析与讨论。【结果】矩形度不随木粉粒径的减小而变化，均值在0.6～0.8之间。长宽比随粒径减小出现先增大后减小的趋势：木粉粒径在1100～576μm 时，长宽比数值从接近于1开始逐渐增大；木粉粒径为576μm时(与本文目标木粉成熟管胞的平均长度563.82μm接近)，长宽比达到最大数值4.6；木粉粒径在576～30μm时，长宽比逐渐减小；而粒径小于50μm 时(与目标木粉成熟管胞的平均宽度46.498μm接近)，长宽比数值再次趋近于1。【结论】长宽比的变化与管胞破裂密切相关：木粉粒径大于管胞长度时，木粉主要通过纵向断裂使粒径减小；粒径与管胞长度接近时，长宽比较大；粒径小于等于管胞宽度范围内，木粉主要是横向断裂，而长宽比基本不再发生变化且趋近于1。长宽比和冲击强度随粒径减小的变化趋势是一致的，长宽比是影响材料力学性能本质因素之一。     

Pulverizing Soils for Laboratory Analysis

Soil-testing laboratories utilize a range of grinder types to pulverize soils for laboratory analysis. This study was conducted to evaluate the effects of soil particle diameter and laboratory subsample size on analysis variability on nitrate, Bray 1 extractable phosphorus (P), extractable potassium (K), and soil organic matter (SOM). Four soils collected for the Agricultural Laboratory Proficiency Program were pulverized using four types of commercial grinders and analyzed for particle-size distribution, P, and K. In a second study, soils were pulverized to pass sieves of 2.0, 1.0, and 0.50 mm and subsampled for P, K, and SOM. Results of the commercial grinders indicate a range in mean particle diameters from 0.15 to 0.60 mm, with the lowest for the grinder utilizing a hammer mill design. Sieve-size analysis results indicate that the coarsest 2.0-mm fraction had the largest variability for all soil analyses evaluated. Analyte variability decreased with decreasing sieve size. Mean Bray P, K, and SOM-LOI (Loss-on-Ignition) mean concentrations were not statistically significantly different across the sieve sizes evaluated. Laboratory analysis variability for extractable Bray P increased as subsample size was reduced.     

种瓣及密度对大蒜产量的影响

采用二次正交通用旋转设计，进行了种辩大小与种植密度对大蒜产量影响的研究，建立了大蒜产量与种植密度及种瓣大小间的二元二次数学模型。通过模型解析得出，种植密度对产量的影响大于种瓣大小，但密度对单株产量的贡献为负值。通过计算机模拟试验，得出本试验条件下，获得３００００ｋｇ／ｈｍ２以上产量的种植密度为５２．９５～６３．４５万株／ｈｍ２、种瓣大小为４．９～７．０ｇ;;单株产量大于５０ｇ的种植密度为３４．０５～４．５５万株／ｈｍ２、种瓣大小４．９～７．０ｇ。     

有风险投资与无风险投资组合的研究

本研究通过引入单位风险的概念，并结合有效边界上的单位风险极小点，给出了各种情况下有风险投资和无风险投资的最优组合方案。