金融危机对中国林产品出口的影响机制

金融危机发生后,中国林产品出口增长几乎处于停滞状态.本文在指出恒定市场份额模型缺点的基础上,提出修正的恒定市场份额模型,并运用修正后的模型分析金融危机影响中国林产品出口的内在机制.结果显示:金融危机冲击下的世界林产品需求萎缩,是中国林产品出口增长几乎停滞的主要原因;而世界林产品需求结构的调整和主要进口市场分布的变化也产生了一定影响.     

小麦K型不育系恢复基因近等基因系农艺性状的遗传差异分析

对近等基因系进行遗传背景检测,有利于选育高质量的近等基因系材料.以17个小麦K型不育系恢复基因的近等基因系(N1～N17)和轮回亲本不育系豫麦3号为材料,通过调查这些材料的株高、成穗数、旗叶长、旗叶宽、倒二叶长、脖长、倒一节长、倒二节长、穗长、小穗数等10个农艺性状.对小麦K型不育系恢复基因近等基因系的农艺性状进行了差异比较和聚类分析.结果表明,连续回交5代后,回交后代与轮回亲本在形态性状上表现出较高的一致性,其中N14、N1、N7、N16和N15与不育系豫麦3号的性状差异较小,在欧氏距离为5.2处把它们聚在同一类,但从各性状的变异系数看,N7和N15自身的变异较大,所以N14、N1和N16与不育系豫麦3号具有较好的近等性.     

Magnetic removal/immobilization of cadmium and zinc in contaminated soils using a magnetic microparticle solid chelator and its effect on rice cultivation

Purpose

Magnetic removal techniques using functionalized magnetic nanoparticles as adsorbents have been frequently tested for use in the removal of heavy metals in aqueous solution, but seldom in farmland soil. Here, a novel magnetic microparticle solid chelator (MSC) was employed as the adsorbent for magnetic removal and/or immobilization of Cd and Zn in a paddy soil (PS), an upland soil (US), and a paddy–upland rotation soil (RS) with different degrees of pollution.

Materials and methods

MSC was applied to 14 kg air-dried soil samples (PS, US, and RS) at the dosage of 1% (w/w), and then watered, and intermittently stirred. Finally, the MSC–metal complexes were retrieved using a magnetic device (MCR treatment) or not (MC treatment), and the removal efficiency of soil Cd and Zn in MCR treatment was evaluated. After magnetic separation of MSC–metal complexes, pot experiments were performed to investigate the impacts of the magnetic remediation process on rice growth, the phytoavailability of soil Cd and Zn, and the accumulation of Cd and Zn in rice plants.

Results and discussion

The MCR treatment exhibited recovery rates of 55.4%, 49.6%, and 19.0% for MSC–metal complexes in PS, US, and RS, respectively, which brought about removal efficiencies of 2.2–12.2% for Cd and 1.9–4.6% for Zn. The MC and MCR treatments substantially decreased the availability of soil Cd, but not soil Zn; this effect was more remarkable when using CaCl₂ instead of DTPA as the extractant for determination of bioavailable metals. Furthermore, the CaCl₂-extractable Cd and Zn had a more significant relationship with Cd and Zn concentrations in rice roots. The MC and MCR treatments led to dramatic reductions in rice grain Cd of 23.9–72.1% and 37.3–63.9%, respectively, in the three soils relative to the respective controls. The MC and MCR treatments also exhibited an inhibitory effects on rice grain Zn accumulation in US (10.6% and 4.3% decreases, respectively) and RS (9.3% and 19.5% decreases, respectively), but not in PS. Moreover, the grain yield was unaffected under the MCR treatment in the three soils, and significantly increased by 29.8% under the MC treatment in US.

Conclusions

Our study suggests that MSC-based magnetic remediation technique can effectively immobilize and/or remove Cd and Zn in farmland soils, decreasing their uptake by rice plants, with no adverse effects on grain yield.

     

球痢清等药物对人工感染兔肠球虫病的治疗比较试验

４８只３０日龄大耳白杂种兔，试验接种感染兔肠球虫的５种混合孢子化卵囊，将球痢清Ｉ、球痢清Ⅱ、莫能霉素和氯苯胍分别拌在饲料中饲喂，以比较其抗兔肠球虫的效果。通过临床观察，分析克粪便卵囊数的变化，记录增重、计算饲料转化率和对每组扑杀兔作病理组织学检查，结果表明：球痢清抑制卵囊产生、减轻肠道病变、增重及饲料转化率的效果明显，与莫能霉素相近，并显著优于氯苯胍。氯苯胍效果较差，几乎与接种不给药组相同。无显著性差异。因此说明氯苯胍不宜单一继续使用。应引入新的高效抗球虫药，并指导正确使用抗球虫药物。     

高阶椭圆锥齿轮泵的流量特性

针对齿轮泵的变量功能及非圆锥齿轮的应用,提出了一种新型相交轴变量齿轮泵——高阶椭圆锥齿轮泵.该齿轮泵是以高阶椭圆锥齿轮为工作转子的非圆锥齿轮泵.根据齿轮的空间啮合原理,给出了其工作转子高阶椭圆锥齿轮副的齿形生成方法.基于该种齿轮特殊的运动学特性,分析了高阶椭圆锥齿轮泵的传动特性,并对其工作结构进行了设计.依据球面微分理论,推导出了高阶椭圆锥齿轮泵的平均理论流量公式、瞬时流量公式以及流量脉动公式,同时分析了高阶椭圆锥齿轮的偏心率、阶数等参数对其流量特性的影响.在同等参数模型及工况条件下,将对高阶椭圆锥齿轮泵的平均理论流量、瞬时流量及其变量范围与圆柱齿轮泵和非圆柱齿轮泵的流量特性进行了对比分析,获得了该锥齿轮泵在同等条件下排量最大、变量范围最大的特点.     

政治文化视野下美国智库的发展和运行

智库在美国的繁荣,离不开美国以参与型政治文化为主导的特定社会环境,二者通过价值取向的趋同实现协同发展。美国政治文化为智库的发展提供文化土壤和精神动力,智库从政策研究型机构到政策推销型机构的转变历程,本质上是以组织机构和实践模式对参与型政治文化做出的响应。研究政治文化与智库间的相互建构和协同发展,可以为我国建设中国特色新型智库提供有益经验。     

玉米低磷响应基因ZmPAP18的表达特征与序列变异分析

紫色酸性磷酸酶(PAP)是金属磷酸酯酶家族的重要成员,在植物对低磷环境适应的过程中发挥重要作用。依据前期构建的低磷胁迫抑制消减文库,运用RT-PCR方法从耐低磷玉米自交系178中克隆了一个酸性磷酸酶基因的全长序列。该基因编码区全长1409bp,其中ORF为1371bp,编码457个氨基酸残基。经保守域分析发现,基因的推测氨基酸序列中含有紫色酸性磷酸酶所特有的5个保守基序和7个金属离子结合位点,属于紫色酸性磷酸酶类,被命名为ZmPAP18。通过实时荧光定量分析表明,ZmPAP18在根和叶中均受到低磷胁迫的诱导增强表达,且在诱导24h后表达量达到峰值;但在玉米根部的表达量高于叶片,表明ZmPAP18在玉米根部可能参与了根外磷素的活化与吸收以及无机磷由根部向其他组织的转运。此外,经序列分析发现,ZmPAP18的3’非翻译区存在一个Indel(TGTTG)位点,并在常用的14个玉米自交系中表现出丰富的多态性,为进一步开发该基因的分子标记及耐低磷种质分子改良提供了参考信息。