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81.
本文介绍一种鉴定青饲料中氰化物的简易方法,此方法所用仪器简单,操作简便、快速、环保,现象明显,效果非常显著。 相似文献
82.
用马尾松毛虫各龄虫口密度的定期调查资料和积温资料,拟合Logistic随机发育模型,结果表明,该模型能精确地描述马尾松毛虫第1代1~6龄幼虫的发育进程。对各龄虫口的时间分布,模型预测值和观察值的吻合程度达90%。对模型参数进行比较表明,除了温度(积温)以外,还有另外一些因素影响着马尾松毛虫的发育进程。 相似文献
83.
我国维生素工业起源于上世纪50年代末,经过近些年的快速发展,目前已经成为全世界能够生产现有全部维生素品种的少数国家之一,同时也是全球最大的维生素出口国之一,相当一些产品的生产工艺及产品质量在国际上处于领先地位。 相似文献
84.
瘤胃灌注不同比例的混合VFA对肉牛瘤胃发酵、能量和氮代谢的研究 总被引:5,自引:2,他引:3
以装有瘤胃瘘管的肉牛(390±30kg)饲喂全羊草的基础日粮,瘤胃灌注4种不同摩尔比例的混合VFA(乙酸:丙酸:丁酸为75∶15∶10,65∶25∶10,55∶35∶10和45∶45∶10),按4×4拉丁方试验设计测定了灌注后代谢产热率(HP/ME),VFA转化为体脂肪的效率(Kf)和可消化氮转化为沉积氮的效率。结果表明,随着灌注混合VFA中丙酸比例超过25%,HP/ME明显降低(P<005),Kf值极显著地增加(P<001);可消化氮转化为沉积氮的效率显著增加(P<005);HP/ME与瘤胃中乙酸比例、Kf值与瘤胃液中丙酸比例均呈线性正相关。 相似文献
85.
Mo Fatemi 《Biological conservation》2009,142(7):1461-1468
Wind-facilitated migration of new genotypes into small, geographically disjunct populations should buffer them against local extinction. Bertya ingramii, a monoecious, wind-pollinated shrub, is restricted to three populations in a 4 km2 area in eastern Australia. Populations are separated by deeply dissected gorges where it is unlikely that seeds are exchanged but where wind movement may facilitate pollen dispersal. Using 156 highly polymorphic ISSR markers, we found moderate genetic variation within and among populations of B. ingramii and less genetic diversity in a nearby and small population of the widespread Bertya rosmarinifolia. The smallest population of B. ingramii (<30 plants) had the highest genetic variation (65% polymorphic markers, Shannon Information Index = 0.30). AMOVA and a Bayesian analysis showed that molecular variance was equally distributed within and among populations suggesting that gene flow is as limited within as in among populations. Genetic distances between populations were only weakly explained by their relative geographic distances (mantel test, R2 = 0.21, P = 0.001) but the distribution of private bands, the departure from Hardy-Weinberg equilibrium, and a UPGMA tree showed that the smallest population of B. ingramii was generally more similar to an upstream population of B. rosmarinifolia. Thirty-eight percent of bands in this small population of B. ingramii were exclusively shared with B. rosmarinifolia. This covert hybridisation may have been an ancient event but may be responsible for contemporary declines in germination and establishment in B. ingramii. The conservation implications are amplified by the endangered status of B. ingramii. 相似文献
86.
肚倍蚜,美灰藓最佳生态条件与肚倍基地建设 总被引:2,自引:0,他引:2
肚倍蚜,美灰藓最佳生态条件研究表明,由光照强度、湿度以及风速等因素决定的环境是制约肚倍丰产、稳产的关键;据此对肚倍基地建设提出若干建议。 相似文献
87.
88.
利用雷州林业局刚果12号桉W5无性系林分中胸径8~18 cm径阶,树高11~23 m的样木1 207株和尾叶桉U6无性系林分中胸径8~18 cm径阶,树高10~21 m的样木784株,按材种规格标准造材实测材积,且分别建立刚果12号桉W5无性系和尾叶桉U6无性系胶合板材立木出材量二元回归方程,经检验精度可靠,可供参考使用。 相似文献
89.
This study established a prediction model for bending properties of glued-laminated timber (glulam) using optimized knot and
modulus of elasticity (MOE) distributions of lumber laminate as the main input variables. For this purpose, knot and MOE data
were investigated for all pieces of lumber that were prepared for glulam manufacturing, and statistical distributions of knot
size, knot number in one lumber, and MOE of each laminate were optimized as distribution functions. These knot and MOE data
were used as input variables in the prediction model for bending properties, and were also used in generating virtual glulam
using the inverse transform method. Prediction of bending properties for glulam was carried out using the transformed section
method, which is partially provided in ASTM D 3737 (Annex A4). Predicted values were compared with those from full-scale four-point
bending tests for 60 six-layered glulams with 10 different laminar combinations. Finally, the allowable bending properties
of glulam for each specific laminate combination were determined by calculating the fifth percentile of the modulus of rupture
and the average modulus of elasticity from virtual test results of more than 1000 virtual glulams. From the results of this
study, predicted bending properties for glulam and their distributions could be used for structural design in both allowable
stress design and limit state design. 相似文献
90.