基于Kendall重现期的华南中小流域洪水峰量联合分布研究

[目的]对山区中小流域洪水峰量联合分布进行研究,以期为山区洪水防治提供理论参考。[方法]基于Archimedean Copula函数与Kendall测度分析3个山区中小流域的洪峰洪量联合分布的3种重现水平。由择优构建的Gumbel Copula及Kendall测度计算了洪水峰量联合分布的"或"、"且"和Kendall重现期及其设计洪水分位数。[结果]①洪峰和洪量之间具有高相关性,Kendall轶相关系数达0.76以上;②3个流域洪水峰量同频遭遇风险概率很大,均超过81%;③在工程经济安全两方面,对比设定的重现期显示,介于"或"重现期和"且"重现期之间的Kendall重现期更准确地反映洪水峰量联合分布的风险率;④按两变量"或"重现期洪水峰量和同频率推算的洪水设计值偏高。[结论]以Kendall重现期推算的洪水峰量设计值,可为山区中小流域防洪工程安全提供新的选择。     

基于Voronoi图的单粒播玉米产量效果的蒙特卡罗模拟

为了明确在单粒播种条件下田间出苗率对玉米产量的影响,以蒙特卡罗二项分布作缺苗模拟,以Voronoi图分配缺苗土地,通过对产量-密度方程进行数学恒等变换计算产量补偿,模拟了2种单粒播策略的玉米产量随出苗率(75%~95%)的变化。结果表明,缺苗斑数目与出苗率呈单峰曲线关系,缺苗斑大小随出苗率呈负指数下降;单粒播造成0.06%~16.78%的减产,且减产率随出苗率下降而增加;两种单粒播策略的产量大小和产量稳定性均有差异,且差异随出苗率下降而扩大。该研究推荐的玉米单粒播策略是:在千方百计提高出苗率基础上,播种的种子数目应当等于目标种植密度除以出苗率、保证出苗的植株数目达到推荐种植密度。该结论对于在玉米生产上广泛采用单粒精量播种具有重要参考价值。     

反复剪切作用下砒砂岩土壤力学性能试验

为分析砒砂岩土壤的力学性能,该文根据砒砂岩土壤的粒径分布特点,对比分析3种不同粒径（≥0.5～1 mm、≥0.25～0.5 mm、＜0.25 mm）,4种不同含水率（5%、8%、11%、14%）土壤试样在法向压力50~300 kPa作用下反复直剪的力学性能,得出以下结论：1）不同粒径的砒砂岩在第1次剪切中剪应力出现峰值,第2、3、4次的剪应力与剪切位移关系曲线呈微硬化型。粒径范围为≥0.25～0.5 mm的砒砂岩峰值强度和残余强度均最低;2）砒砂岩随含水率增加,峰值强度和残余强度均有所降低。粒径范围为≥0.5～1 mm的峰值强度和残余强度受含水率影响最显著;3）进一步拟合得到了砒砂岩法向位移和剪切位移的函数关系,可以较好地反应砒砂岩剪切过程的剪胀规律。该研究为砒砂岩区水土流失及边坡稳定问题的防治提供力学依据。     

向日葵菌核病菌核及子囊柄萌发峰期的预测

向日葵菌核病的流行取决于田间菌核量与气候因素的影响。试验研究得知,菌核子囊柄萌发程度在菌核经过一场透雨后与七月底,八月份的降雨量及降雨次数呈正相关,而与此时期的平均温度,降雨间隔期呈负相关。由此建立了预测菌核子囊柄萌发程度的多元回归式为y=65.25—2.58x_1 0.04x_2 2.36x_3-2.10x_4。子囊柄萌发期是进行药剂防治的最有效时期,因此预测子囊柄萌发峰期是防治菌核病的关键。通过多元回归建立预测式为y=76.52-1.38x_1 0.06x_2-1.84x_3-3.86x_4。用上述两式回测前2年的田间实测值其结果与预测值极近。     

Corn Genotypic Variation Effects on Seedling Emergence and Leaf Appearance for Short-Season Areas

Identifying corn ( Zea mays L.) genotypes with faster rates of seedling emergence and leaf appearance is important in developing a corn crop with earlier canopy closure and better seasonal light interception. A greenhouse experiment was conducted twice to investigate whether corn genotypes known to vary in canopy architecture and yield potential differed in rates of seedling emergence and leaf appearance. The experiment was arranged in a randomized complete block design utilizing seven genotypes: five of the newly developed Leafy reduced-stature (LRS) types (LRS1, LRS2, LRS3, LRS4 and LRS5), one conventional type [Pioneer 3979 (P3979)], and one late-maturing big-leaf (LMBL) type. Five seeds were planted in each pot and seedling emergence was recorded every day until all seeds emerged. Leaf appearance was recorded from seedling emergence until the plants reached anthesis. There was variability among the genotypes for both seedling emergence and leaf appearance rate. Mean seedling emergence values of greater than 90 % were achieved by four of the five LRS genotypes, and the LRS types generally emerged more rapidly than the others. Leaf appearance rate showed linear increases over time; however, LRS genotypes (in particular LRS3, LRS4 and LRS5) had more rapid leaf appearance rates than the others. The LMBL hybrid ranked last for both seedling emergence (<80 %) and leaf appearance rate. Rapid seedling emergence and leaf appearance by early-maturing genotypes (LRS and P3979, especially LRS) may help these types of genotypes achieve earlier canopy closure and better use of the light available during the growing season, which is critical in a short growing season environment.     

Effect of Seed Pre-sowing Hardening on Physiological Behaviour and Seed Yield of Berseem (Trifolium alexandrinum L.) Crop

A field experiment was conducted at Central Research Farm, Indian Grassland and Fodder Research Institute, Jhansi to study the effect of seed pre-sowing hardening on seed emergence, physiological behaviour — and seed yield of berseem ( Trifolium alexandrinum L. Var. S-99-1) crop. For this purpose, seed pre-sowing hardening were made by soaking of seeds in tap water for 24 and 36 hours separately and later dried back to their original weight or left undried. These seeds were sown at two depths (5 and 3 cm) and judged against control (no soaking). Results demonstrated that augmented effect of seed hardening on seed emergence and physiological process responsible for seed yield was recorded in descending order of harden seeds (of 24 hours soaking) > non harden seeds (of 24 hours soaking) > harden seeds (of 36 hours soaking); while non-harden seeds of 36 hours soaking adversely affect the plant growth because of leaching of sugar during excess soaking — an element for reduced seed vigour potential. Seed hardening system developed the strength of seed emergence on account of efficient catabolic process releasing high water soluble sugars needed for efficient germination process. Further this process augmented the absorption mechanism of mineral nutrients (particularly phosphorus and nitrogen with marginal variation in calcium) was quite evident at bloom stage — indicating a high metabolic activity during this period. Performance of seed hardening was effective at 5 cm deep sowing.     

Investigation of the immediate analgesic effects of extracorporeal shock wave therapy for treatment of navicular disease in horses

OBJECTIVES: To measure the acute analgesic properties of extracorporeal shock wave therapy (ESWT) in horses with navicular disease using objective ground reaction forces (GRF). STUDY DESIGN: Prospective study. ANIMALS: Nine client-owned horses with unilateral forelimb lameness caused by navicular disease. METHODS: Horses were trotted at 3 m/s over a force plate to record pre-treatment GRF of the lame and contra-lateral forelimbs. After ESWT of the lame limb, applied with a radial unit to each of the frog and heel bulb areas with 1500 pulses at 4 bar and 10 Hz, GRF measurements were repeated at 15 minutes and 24-hour intervals for 7 days. From the 5 trials recorded at each time, peak vertical force (PVF) was calculated and averaged. Data were compared between limbs and over time using a 2-way repeated-measures ANOVA. RESULTS: Mean (+/-SD) PVF was significantly different between lame (day 1; 4339+/-626 N) and contra-lateral (day 1; 5236+/-515 N) limbs pre-treatment (P<.05). After ESWT treatment, this difference remained unchanged at 15 minutes and from days 1 to 7. To confirm navicular disease, palmar digital analgesia significantly reduced the lameness (lame 5144+/-430 N; contralateral 5082+/-586 N; P>.05). CONCLUSIONS: Single ESWT treatment applied in this manner does not influence lameness in horses with navicular disease. CLINICAL RELEVANCE: Although many equine regulatory commissions currently ban the use of ESWT before competition, our results suggest that such regulations may be unfounded. Further research is required to determine the long-term analgesic properties of this frequently used treatment modality in equine athletes.     

Accuracy and optimization of force platform gait analysis in Labradors with cranial cruciate disease evaluated at a walking gait

OBJECTIVE: To determine the combination of ground reaction forces (GRFs) that best discriminates between lame and non-lame dogs. To compare the sensitivity of force platform gait analysis and visual observation at detecting gait abnormalities in Labradors after surgery for rupture of the cranial cruciate ligament (CCL). ANIMALS: All dogs were adult Labrador Retrievers: 17 free of orthopedic and neurologic abnormalities, 100 with unilateral CCL rupture, and 131 studied 6 months after surgery for unilateral CCL injury, 15 with observable lameness. PROCEDURE: Dogs were walked over a force platform with GRF recorded during the stance phase. Analytic properties of force platform gait analysis were calculated for several combinations of forces. The probability of visual observation detecting a gait abnormality was compared with that of force platform gait analysis. RESULTS: We determined that a combination of peak vertical force (PVF) and falling slope were optimal for discriminating sound and lame Labradors. After surgery, many dogs (75%) with no observable lameness failed to achieve GRFs consistent with sound Labradors. CONCLUSION: A force platform is an accurate method of assessing lameness in Labradors with CCL rupture and is more sensitive than visual observation. Assessing lameness with a combination of GRFs is better than using univariate GRFs. CLINICAL RELEVANCE: Therapies for stifle lameness can be accurately and objectively evaluated using 2 vertical ground reaction forces obtained from a force platform.     

山东泰安地区小麦禾谷孢囊线虫幼虫孵化特性初步研究

为大量获得研究所需的小麦禾谷孢囊线虫2龄幼虫,在室内离体条件下研究了预处理条件、孵化温度、低温预处理时间以及田间采样时期对山东泰安地区小麦禾谷孢囊线虫幼虫孵出量的影响.结果表明:5℃低温预处理条件下,孢囊浸水处理有利于幼虫孵出;低温预处理后,孵化温度为15℃处理的2龄幼虫孵出率高于20℃处理的孵出率;低温预处理时间为8周的2龄幼虫孵出率最高;6月和8月田间采集的孢囊幼虫孵出率显著高于7月和9月,其中8月采集的孢囊幼虫孵出率最高,为最佳采集时间.     

黑条帕寄蝇成虫生物学特性初步研究

黑条帕寄蝇(Palesisa nudioculla Villeneuve)是草地螟(Loxostege sticticalis L.)及其他许多鳞翅目害虫的重要寄生性天敌,国内外对其研究报道较少。通过田间调查和室内试验研究了黑条帕寄蝇成虫主要的生物学特性,为该蝇种的保护利用奠定基础。结果表明:黑条帕寄蝇的寄生方式属微卵生型,羽化时间主要集中在每天的08:00-10:00,16:00-18:00,羽化性比为1.13∶1(雌∶雄),且雄蝇比雌蝇先羽化;在条件为(23±1)℃、L∥D=16h∥8h、RH 60%～70%的光照培养箱中饲养,成虫的寿命最长,可达34d;以含糖物质补充营养能延长成虫的寿命,特别是20%的蜂蜜水补充可显著延长其寿命,且雌蝇比雄蝇的寿命长;被寄生的草地螟虫茧低温(4℃)储存20d后的羽化率没有显著变化,但随着储存时间的增加羽化率显著降低。