狗牙根果岭的交播技术

主要介绍狗牙根果岭的交播技术 ,包括草种选择和配比、种子直播、交播前后的管理措施 ,并讨论了狗牙根果岭的春季过渡技术等。     

农牧交错带农牧系统氮素流动与环境效应——以山西省为例

【目的】探明山西省农牧交错带农牧生产系统的氮素流动特征及其环境效应,进一步为山西实施区域养分资源管理、加快农牧交错带产业结构调整提供科学依据。【方法】在整理统计资料、文献数据和实地调研的基础上,使用食物链养分流动模型（nutrient flows in food chains, environment and resources use,NUFER）和GIS,估算山西省农牧交错带（主要涉及大同、朔州、忻州、吕梁、临汾和太原等6个地市）42个县区农牧生产系统的氮素账户平衡、流动路径及损失途径。【结果】不同县区农田化学氮肥投入存在“两极分化”的现象,投入水平范围在6.7-253 kg·hm^-2,极值间相差38倍;各县区农田氮素的投入结构也表现出较大差异,主要跟当地化学氮肥施用习惯及农业种植结构有很大的关系;单位农田面积农作物主产品的氮素携出量范围在19.11-96.75 kg·hm^-2,空间上整体呈现南北高、中部低的变化趋势;不同县区农田氮素盈余量在-16-202 kg·hm^-2,氮素亏缺与盈余情况并存;区内畜牧生产系统中外源饲料氮素投入差异较大,朔州市的山阴县外源饲料氮素投入高达0.94×10⁴ t,而忻州的五寨、临汾的隰县、大宁和蒲县,则可以通过作物生产系统来满足畜牧生产系统的饲料需求,也充分反映了各县区畜牧业养殖规模和农牧产业结构存在较大差异;区内单位面积农田动物主产品氮素携出量范围在1.51-27.50 kg·hm^-2,极差25.99 kg·hm^-2,说明各县区畜牧生产系统的生产力水平差异较大,单位农田面积动物主产品的氮素携出量＞13 kg·hm^-2的分布在区域北部朔州市的山阴、怀仁、大同等县区,表明这些县区畜牧生产系统中的氮素利用率较高;单位耕地面积畜禽粪尿氮素负荷较高（＞50 kg·hm^-2）的县区主要分布在区域北部;农牧生产系统氮素损失的空间分布格局明显：一级区（＞200 kg·hm^-2）分布在区域北部,二级区（120-200 kg·hm^-2）分布在区域南部和北部,三级区（＜120 kg·hm^-2）主要分布在区域中部,今后应重点关注区域北部农牧业生产过程中的氮素损失及环境问题。【结论】农业生产结构不合理、“农牧分离”是造成农牧生产系统氮素利用率低下的主要原因,今后农田养分资源综合管理要在空间上合理配置氮素资源,在养分投入上既要考虑化学氮肥和粪尿氮素的投入,还要兼顾来源于环境投入部分的氮素,更要注重和畜牧生产系统的耦合,以最小的环境代价生产更多的农牧产品。     

液压机械全功率换段方法及功率过渡特性

为了解决液压机械无级传动换段过程中存在的动力中断和换段冲击等问题,基于当前段与目标段双制动器结合重叠,提出全新的液压机械全功率换段方法,并深入探究全功率换段过程功率过渡机理及控制方法。该文以两段等差式液压机械为研究对象,在双制动器结合重叠的动力换段方式的基础上,提出了五阶段液压机械全功率换段方法,通过理论分析与试验相结合的方法,研究了换段过程中液压机械转矩特性和功率特性随液压回路压差的变化规律,液压回路压差随变排量液压元件排量的变化规律。结果表明,在双制动器结合重叠的动力换段中,通过调节变排量液压元件的排量比,能够控制液压回路的高低压侧压差改变、互换,进而控制当前段制动器转矩向目标制动器有序转移,在双制动器结合重叠中完成换段,实现换段过程传递全功率。输入转速保持1 000 r/min不变,进出换段时定排量液压元件转速无波动,输出扭矩波动量约为5 N·m(负载扭矩为60 N·m和150 N·m)。该研究揭示了液压机械全功率换段的功率过渡机理,可为全功率换段的后续研究及液压机械应用提供了参考。     

含气率对小流量下混流式混输泵轴系振动的影响

振动是反映混输泵运行稳定性的关键指标,液体含气率对混输泵的振动强度有重要影响.为探究小流量工况下含气率变化对混输泵轴系振动的影响规律,该研究以某3级混流式气液混输泵为研究对象,采用建立的多通道振动测试系统采集小流量工况下混输泵输送不同含气率的水时主轴和轴承座的振动信号,然后分析水中含气率对主轴和轴承座振动特性的影响规律...     

Unravelling transcriptome changes between two distinct maize inbred lines using RNA-seq

Seed size play a significant role in maize yield production. Two maize inbred lines with distinct seed size and weight, V671 (a large-seed inbred line) and Mc (a small-seed inbred line), were investigated by RNA-seq at 14 days after pollination (DAP), when maize endosperm undergoes an active transition from mitosis to storage accumulation. RNA-seq expression data showed that the small-seed line Mc had a higher storage accumulation activity, whereas the large-seed kernel line V671 possessed a higher DNA synthesis activity. An investigation of the pattern of increasing kernel width at serial DAPs showed that V671 experienced an increased kernel width later than did Mc, but the rate and duration of increase were longer in V671. SDS-PAGE of the storage proteins and quantitative RT-PCR of cell cycle-related genes and indole-3-acetic (IAA) synthesis genes certified that the transition from mitosis to storage accumulation starts earlier in Mc. We hypothesized that the difference in the mitosis-to-storage accumulation transition accounts for the larger seed size in V671 vs. Mc.     

Ground-active arthropod response to distance from the Mediterranean seashore in coastal sand areas of western Israel

Information on the effects of distance from the seashore on soil biotic communities is limited and restricted to soil arthropods and microarthropods. The aim of this study, conducted in a sand-dune area, was to distinguish the changes of a ground-active arthropod community along a 4-km-transect from the seashore going inland. Pitfall traps were set up in open spaces at four locations (L1, through L2, L3, and L4 going inland) through the year. The abiotic gradient from the seashore going inland was found to be mostly dependent on seasonality. Group richness was found to be remarkably greater at the L2, L3, and L4 locations compared with the L1 location in winter, and at the L2 and L3 locations compared with the L1 location in spring. The Fisher α index was 0.32?±?0.21, 3.51?±?0.87, 5.04?±?0.70, and 4.86?±?0.54 in winter and 3.29?±?0.55, 13.79?±?1.49, 10.12?±?1.24, and 5.06?±?0.62 in spring at the L1, L2, L3, and L4 locations, respectively. Regarding abundance and group richness, the trophic relationships between predators, phytophages, omnivores, and saprophages were remarkably affected by both location and seasonality. The dominant groups and dominant index distribution of ground-active arthropod communities were found to follow a similar pattern. Soil organic carbon content was found to be the key factor driving the ground-active arthropod community structure along a coastal gradient going inland in winter and spring. We conclude that the distribution, trophic composition, and diversity index are affected by both location and seasonality, while total abundance is consistently affected by location across all three seasons.     

论农地规模经营的一般规律及发展前景

分析研究了人口、生态和技术的变迁对农地规模经营的影响。在长期的历史变迁中，中国农业的发展在人口压力下形成了与追求产量最大化相一致的小规模经营，且随着集约化技术的发展，小规模经营愈加强化。技术变迁的历史表明：完善的市场化措施和社会化服务体系的建立，完全可以在目前小农经营基础上改造传统农业并促进农业生产的进一步发展。     

无籽西瓜胚轴维管束转位的观察

借助石蜡切片技术对无籽西瓜胚轴进行连续切片和系统镜检。在根茎过渡区连续横切面上,可看到由根部四原型外始式初生木质部与初生韧皮部相间排列的维管束转变到茎部成为四原型、内始式和双韧并生排列的维管束。转化经过分叉、倒转和合并,是不同步的,从左到右沿顺时针力向逐步转变。中胚轴子叶迹发生处延伸出2个小束。根、茎维管束转换区发生在下胚轴。该区外形较粗大,生理活性较强,对外界条件变化较敏感,是瓜苗抗性最弱部位,也是组培择取外植体最合适的节段。可为瓜苗耕作管理和择取外植体提供形态学参考指标。     

Protective role of 14-3-3γ in burn and LPS-induced rat myocardial injury

AIM: To study the protective role of 14-3-3γ in burn or LPS-induced myocardial injury. METHODS: The rat model of burn or LPS-induced injury was established. The heart functions and 14-3-3γ protein expression were detected 3 h, 6 h, 12 h and 24 h after treatment. Primary neonatal rat cardiomyocytes were used in vitro. pFLAG-14-3-3γ plasmid was constructed and transfected into the cardiomyocytes 24 h before LPS-induced injury. The injury in the cardiomyocytes was evaluated by measuring the cell viability and the level of lactate dehydrogenase(LDH). Apoptosis of cardiomyocytes was detected by flow cytometry. Opening of mitochondrial permeability transition pore (mPTP) was also determined by Ca²⁺-induced swelling of isolated myocardial mitochondria. RESULTS: The expression of 14-3-3γ was elevated following the burn or LPS-induced myocardial injury in vivo. In vitro, transfection with pFLAG-14-3-3γ plasmid in to the cardiomyocytes significantly protected against LPS-induced injury. Compared with the cardiomyocytes without transfection with pFLAG-14-3-3γ plasmid, higher cell viability rate and lower LDH release, cell apoptosis and mPTP opening were observed in the cardiomyocytes transfected with pFLAG-14-3-3γ plasmid. CONCLUSION: The 14-3-3γ protein protects the heart against burn or LPS-induced injury by inhibiting the mPTP opening.     

新农村建设中农户的居住生活变化及其生计转型

农户生计问题是政府和学界关注的焦点.采用参与式农村评估法,对新农村建设热点区域邛崃市的典型村进行了实地调查和分析,结果发现:①农村居民点是一个与农户生计息息相关的多功能复合单元.②新居建设改善了农户的居住区位和生活条件,但功能趋于单一化;按照城市的居住生活习惯设计新居的功能结构,导致农村居民点用地大幅减少.③土地整理新增耕地和因迁建而得的新居房产,是农户新获取的重要物质资产;利用掌握的社会资产寻找非农就业机会、拓展就业渠道对农户改善生计至关重要.由于普遍缺乏高质量的人力资产,农户实现生计多样化仍要克服许多困难;随着庭院经济的没落,农户生活资料的市场依赖性日趋增大,传统的家庭农具面临贬值、淘汰;在物质资产减少、家庭负担加重、收入缺少增长的处境下,政府的金融性资产支持难以促进农户金融资产的增长.④居住生活方式和生计资产的变化直接或间接地引起农户生计转型,呈现"正面的非农化"和"负面的非农化"两种趋向.⑤新农村建设照搬城市的居住生活方式对农户缺乏现实意义,可能背离了此项决策的初衷.建议地方政府依据农户的家庭状况和发展需求,分类指导,设计不同的政策细节,为农户创造适宜的发展机会.