保护性耕作推广中的制约因素及其对策

在保护性耕作的推广过程中存在技术、经济、文化三个方面的制约因素,它们降低了保护性耕作的发展速度。这三个方面因素有着内在联系,他们的影响通过机具数量不足的形式表现出来。本文分析了这些因素的影响,提出了相应的解决措施。     

Comparative Analysis of Photosynthetic Parameters and its Evaluation in Pearl Millet Hybrid and its Parents

Fully expanded leaf occupying topmost position in a field grown pearl millet hybrid (BJ-104) and its parents (J-104 and 5141-A) were analysed at weekly intervals for chlorophylls, Hill activity and phosphoenolpyruvate carboxylase activity. Large ontogenic drifts in these parameters, made the actual comparison between hybrid and parents, difficult. However, up to 52 d the hybrid leaf possessed considerably higher chlorophyll pigments than its parents. Amongst the inbreds, the male parent was initially better than the female parent while at later stages, the trend was reversed. Hill activity and PEPcase were more in the male than in the female parent and the hybrid followed the better parent. Rate limiting steps for productivity, measured as NAR (g dry weight)⁻¹, were worked out in the female parent, using multiple regression and correlation analysis, and the significance of such an analysis is discussed in relation to plant productivity.     

果树生产技术经济效果评价的理论

本文从技术经济学的理论出发,论述了果树技术经济效益概念,果树技术经济效益的特点,详细阐述了果树生产技术经济效果评价的内容,评价应遵循的基本原理和评价的标准     

Enzymes of Ammonia Assimilation and Transamination in Relation to Hybrid Vigour in Pearl Millet (Pennisetum americanum L. Leeke)

Changes in the activities of enzymes of ammonia assimilation viz., glutamate dehydrogenase (GDH), glutamine synthetase (GS) and glutamate synthase (GOGAT), together with the activities of glutamate oxaloacetate transaminase (GOT) and glutamate pyruvate transaminase (GPT) were analysed in the topmost fully expanded leaf of pearl millet (Pennisetum americanum L. Leeke) hybrid BJ-104 , and its parents, J-104 and 5141-A , during the entire period of growth in field. Ammonia assimilation enzymes showed strong ontogenic trends and the hybrid attained activities either equal to the better (male) parent or showed better parental heterosis. In contrast to this both GOT and GPT activities were slightly higher than the poor (female) parent. The role of these enzymes in relation to chlorophyll synthesis and transport of metabolites from cellular compartments of C₄ plants, are discussed. Surveying the literature on attempts to propose biochemical criteria for hybrid vigour, it is proposed that there cannot be a universal criterion, rather rate limiting steps in different cultivars should be searched.     

木结构在中国

本文阐述了现代木结构建筑在中国的应用、研究现状、建筑实例,指出木结构在我国具有很大的潜在市场,并且有利于合理有效的利用我国的林木资源,生产出具有高附加值的产品,做到经济、社会、生态效益的三者相统一。     

天津市海河教育园区土壤生态系统保育及修复

以天津市海河教育园区为例,探讨土壤生态系统保育及修复在盐碱地园林绿化中的重要作用。所以,在已建园区,要时时监控土壤盐分的动态变化,通过合理的灌溉方式防控土壤次生盐碱化;在未建园区,应用基于土壤盐分空间分布的综合改土技术、自然景观的土壤排盐系统,来减少土壤盐害,并通过土壤生态条件的空间变异来优化植被类型分布及景观格局,最终实现生态功能的可持续化。     

非线性二阶阻尼微分方程的区间振动准则

给出非线性二阶阻尼微分方程新的振动准则,它们仅依赖于区间[t0,∞)的某些子区间序列的信息,不需要依赖于整个半直线,所得结果推广和改进了某些最近的结果.     

Employing a Monte Carlo algorithm in expectation maximization restricted maximum likelihood estimation of the linear mixed model

Multiple‐trait and random regression models have multiplied the number of equations needed for the estimation of variance components. To avoid inversion or decomposition of a large coefficient matrix, we propose estimation of variance components by Monte Carlo expectation maximization restricted maximum likelihood (MC EM REML) for multiple‐trait linear mixed models. Implementation is based on full‐model sampling for calculating the prediction error variances required for EM REML. Performance of the analytical and the MC EM REML algorithm was compared using a simulated and a field data set. For field data, results from both algorithms corresponded well even with one MC sample within an MC EM REML round. The magnitude of the standard errors of estimated prediction error variances depended on the formula used to calculate them and on the MC sample size within an MC EM REML round. Sampling variation in MC EM REML did not impair the convergence behaviour of the solutions compared with analytical EM REML analysis. A convergence criterion that takes into account the sampling variation was developed to monitor convergence for the MC EM REML algorithm. For the field data set, MC EM REML proved far superior to analytical EM REML both in computing time and in memory need.     

Canine neurogenic Keratoconjunctivitis sicca: 11 cases (2006-2010)

Objective To describe the clinical data of dogs with neurogenic Keratoconjunctivitis sicca (KCS) and an ipsilateral dry nose without other neurologic deficits. Procedure The retrospective case study included 11 dogs diagnosed with neurogenic KCS and an ipsilateral dry nose between 2006 and 2010. Medical records were reviewed for breed, age, sex, history, suspected cause of neurogenic KCS, clinical signs, and treatment modalities. Follow‐up information was obtained by re‐examination of patients or completion of a telephone survey with the referring veterinarian or the owners. Results Mean age of the dogs was 6.6 ± 4.5 years. Neurogenic KCS was diagnosed in three females, five spayed females, one male, and two castrated males representing 10 different breeds. Ophthalmic signs of KCS (mean Schirmer tear test [STT] value of 1.9 ± 2.9 mm/min) combined with an ipsilateral dry nose were diagnosed in seven left and four right eyes. The suspected cause of neurogenic KCS was idiopathic in nine and trauma in two cases. Systemic therapy consisted of oral pilocarpine 1–2% eye drops combined with case‐specific topical treatment with cyclosporine 0.2% and tear substitutes. Duration of systemic treatment with pilocarpine until healing was 125 days (range 84–204, median 98 days) for five dogs. One dog was lost to follow‐up, and the remaining five dogs are still under systemic treatment with pilocarpine. Conclusions Neurogenic KCS with an ipsilateral dry nose seems to be a predominantly idiopathic disease of middle‐aged female dogs without breed predisposition, which may be self‐limiting in some cases.     

根—土复合体强度及其非线性特性试验研究

[目的]研究根—土复合体的非线性破坏准则,并结合不同含根量(G=0.12%,0.24%,0.36%)、不同含水率(w=13.22%,16.22%,19.22%)条件下根—土复合体强度,开展根—土复合体非线性特性研究,为生态水土防治工作提供科学参考。[方法]采用GDS三轴仪开展了根—土复合体的固结不排水三轴试验,获得根—土复合体应力—应变曲线及抗剪强度指标。[结果]素土与根—土复合体应力—应变关系曲线为硬化型。含根量与根—土复合体峰值强度成正比关系,但含水率对其峰值强度的影响表现出反比关系。当G=0.36%时,根—土复合体峰值强度的最大增幅为70.1%;当w=13.22%时,根—土复合体峰值强度最大增幅为86.7%。根—土复合体非线性破坏准则在正应力低于临界应力时呈非线性,在正应力高于临界应力时呈线性。c,k为根—土复合体非线性破坏准则中描述根系作用的关键参数,其中c与含根量和含水率均成正比关系,c越大,根系对根—土复合体强度的贡献程度越大;k与含根量成反比,与含水率成正比,k越小,根—土复合体强度包线的非线性化特征越明显。[结论]含根量(G)和含水率(w)对根—土复合体强度有显著影响。...