Seasonal forcing on the dynamics ofClethrionomys rufocanus: Modeling geographic gradients in population dynamics

We interpret gradients in population dynamics of the gray-sided vole from the southwestern part of the island of Hokkaido to its northeastern part within the framework of a phenomenological model involving the relative length of summer and winter. In Hokkaido, as in other northern regions, both spring and fall is considered as short transition periods between the two main seasons — summer (the primary breeding season) and winter (the non-reproductive or secondary breeding season). We show that the geographic transition in dynamics may be understood as the combined consequence of different patterns of density-dependence during summer and winter, and geographically varying season lengths. Differences are shown to exist between summer and winter with respect to strength of density-dependence. Direct density-dependence, in particular, is stronger during winter than during summer. A model is presented to show how relative lengths of seasons can induce both stable and periodically fluctuating population dynamics. The results are compared and contrasted with what is otherwise known about the gradient in rodent dynamics in Fennoscandia.     

平武山区生态特点及对杂交玉米的要求

分析了地处盆周山区的平武县的地貌、土地、土壤、气候的概况及特点，讨论了山区特殊生态环境条件对玉米生长发育及产量的影响，提出了适应山区环境条件的玉米杂交种应具有的特点。     

关于农业政策性银行职能定位的思考

农业政策性金融,其主要是农业发展银行肩负着政策性支农的重任,在国家的宏观调控中发挥着重要作用。农业政策性银行(简称农发行)要在构建农业特别是粮棉油产业投入稳定增长的机制的同时,使“三农”特别是粮食增产和农民增收以及粮棉油产业化经营得到更稳定的资金支持。农业发展银行应围绕大粮食大产业,努力办成支持粮棉油产业发展的银行。要实现这种定位,农发行必须在着力经营有效资产的基础上,创新信贷管理方式,把营销的出发点和归宿放在逐步建立优质稳定的客户群体上,强化与中央银行和国家财政的关系,构建完善的业务发展支撑体系。     

中美玉米期货市场风险溢出效应研究

为研究中美玉米期货市场风险溢出效应的方向和大小,选取2006年1月4日至2017年5月31日大连商品期货交易所和芝加哥商品交易所中的玉米主力连续价格以及央行外汇中间价的日数据为样本数据,并将样本期间分为3个阶段,借助平稳性检验、相关性检验,采用EGARCH-GED模型、VaR模型和格兰杰因果检验来研究两市玉米期货的风险溢出效应。研究发现,中美两国玉米期货市场的风险存在正相关性,且在金融危机期间风险相关性明显增强并存在双向的风险溢出效应;在金融危机之前,美国玉米期货市场对中国玉米期货市场有风险溢出效应。     

我国生猪市场价格调控中的"猪粮比价":理论内涵与实践反思

无论从稳定生猪生产和农民增收,还是从保障居民的猪肉消费,生猪市场的重要性都是不言而喻的.2007年以来,我国政府逐步形成了一整套依据"猪粮比价"高低进行价格干预的制度安排.然而,学术界却并没有深究"猪粮比价"这一指标背后的经济逻辑.文章尝试推导出了"猪粮比价"的理论公式,发现"猪粮比价"等于生猪养殖中技术口径的投入产出效率与经济口径的投入产出效率之比值.与此同时,还发现在会计核算和经济核算两种口径下有着不一样的计算结果.通过简要回顾我国政府根据"猪粮比价"对生猪市场进行价格调控的历程,发现价格干预的效果并不尽如人意.对比理论公式和价格干预实践,文章找到了导致以上结果的原因.事实上,美国农业部虽然也公布"猪粮比价",但却并没有将之用于指导猪肉市场的价格调控.     

Effects of a summer emergent literacy intervention for rising kindergarteners

This study examined the effectiveness of a nine-week summer emergent literacy program implemented in a Young Men's Christian Association (YMCA) summer program that serves families from low socioeconomic backgrounds. Participants were four- and five-year-old children attending a YMCA summer camp. After being placed in appropriate respective skill-level groups, children received one-hour, daily emergent literacy instruction from their camp counselors, who were trained as novice reading teachers. The teachers used emergent literacy activities to support letter-naming fluency and growth in letter-sound correspondence recognition in addition to mastery of read-aloud texts. The 28 participants experienced positive growth on both dependent measures (letter-naming fluency and letter-sound fluency), indicating the efficiency of the intervention as a tool for improving school readiness for children from low-income families. Additionally, the results suggest that beginning reading teachers may be able to conduct effective emergent literacy instruction, making the intervention replicable. Limitations and associated future research directions are discussed.     

杂交玉米高产制种技术研究

该项研究宗旨是探索雷州半岛杂交玉米高产制种的可行性及其配套制种技术．经过两年三造的试验研究,其主要经济技术指标达到预期效果．累计面积２６ ．９ 亩．组合为南试８４７ ,加权平均亩产量为２３７ ．１ ｋｇ,最高亩产３００．１ ｋｇ．根据研究结果,本项目初步总结出了南试８４７ 组合杂交制种配套技术,为指导玉米制种提供了理论依据和实践经验．     

施肥对冬小麦和夏玉米氨基酸和蛋白质含量的影响

在肥料长期定位试验的第9年、10年、11年,测定冬小麦和夏玉米籽粒蛋白质及17种氨基酸含量,氮钾肥配合施用,冬小麦氨基酸总量较对照提高40.29%,苏氨酸、丝氨酸、甘氨酸、丙氨酸、异亮氨酸、苯丙氨酸、赖氨酸含量提高25.92～38.23%。高量有机肥和高量氮肥相配合,冬小麦蛋白质含量较对照提高49.44%,并且蛋白质含量与产量呈显著正相关(r=0.6301);夏玉米氨基酸总量较对照增加41.92%,苏氨酸、丝氨酸、谷氨酸、丙氨酸、亮氨酸增加33.33%～65.71%,蛋白质含量增加31.30%,蛋白质含量与产量呈极显著正相关(r=0.7552)。施肥对冬小麦和夏玉米蛋氨酸和脯氨酸含量的影响不显著。     

从谷物模型看李嘉图价值与分配理论

讨论了简单的谷物模型和扩展的谷物模型。在简单的谷物模型中 ,进一步论证了李嘉图关于工资与利润的对立关系。通过将实物形态的谷物模型转化为价值形态的谷物模型 ,也分析了李嘉图的商品价值决定于边际劳动成本这一命题。在扩展的谷物模型中 ,通过引入生产资料 ,说明李嘉图价值难题的形成。