3种木兰科植物聚合果轴的比较解剖

对木兰科Ｍａｇｎｏｌｉａｃｅａｅ中华木莲Ｓｉｎｏｍａｎｇｌｉｅｔｉａ ｇｌａｕｃａ Ｚ．Ｘ,Ｙｕ,ｅｔ Ｑ．Ｙ．Ｚｈｅｎｇ,乳源木莲Ｍｏｎｇｌｉｅｔｉａ ｙｕｙｕａｎｅｎｓｉｓ Ｌａｗ和白玉兰３种植物从开花至聚合果成熟期的着生心皮的心,果轴进行横切制片的比较解剖观察,主要特点是：开花期－３种植物的花轴无明显差异。幼果期－３种植物聚合果轴中维管束数目依次为２６￣２９、１７￣１９和１１￣１２束;华木莲     

银杏胚轴、子叶诱导胚状体发生及成苗的研究

银杏 (Ginkgobiloba)素有裸子植物“活化石”之称 ,在植物学上具有重要的研究价值 ;同时银杏的经济价值也很高 ,既可作为园林绿化树种 ,也是优良用材树种 ,且其种子、叶片富含营养与药用成分 ,用途广泛。然而银杏是雌雄异株植物 ,实生苗定植后一般需要 2 0～ 30a才能开花结果、分出雌雄 ,常规育种时间长、效率低。栽培过程中结实晚 ,早期收益低。因此应用生物技术改良品种和进行优良品种的快繁 ,前景都十分广阔。 2 0世纪 30年代以来 ,银杏组织培养主要以胚 (Li,1934)、配子体 (Tulecke ,195 7;Rohr ,1980 )及营养器官(罗紫娟 ,1985 )为材…     

Microbiota-gut-brain axis and nutritional strategy under heat stress

Heat stress is a very universal stress event in recent years. Various lines of evidence in the past literatures indicate that gut microbiota composition is susceptible to variable temperature. A varied microbiota is necessary for optimal regulation of host signaling pathways and disrupting microbiota-host homeostasis that induces disease pathology. The microbiota–gut–brain axis involves an interactive mode of communication between the microbes colonizing the gut and brain function. This review summarizes the effects of heat stress on intestinal function and microbiota–gut–brain axis. Heat stress negatively affects intestinal immunity and barrier functions. Microbiota-gut-brain axis is involved in the homeostasis of the gut microbiota, at the same time, heat stress affects the metabolites of microbiota which could alter the function of microbiota–gut–brain axis. We aim to bridge the evidence that the microbiota is adapted to survive and thrive in an extreme environment. Additionally, nutritional strategies for alleviating intestinal heat stress are introduced.     

具有多模式球面4R机构结构参数研究

基于代数几何理论,结合双变量代数方程可因式分解的判定条件,对球面4R机构运动学方程进行研究,提出一种确定具有多模式球面4R机构结构参数的分析方法.可得5类具有约束奇异位形的球面4R机构,其中多模式球面4R机构可分为4类:具有定轴线和变轴线2种转动运动模式,具有2种变轴线转动运动模式,具有1种变轴线和2种定轴线3种转动运...     

基于离散元的双轴旋耕机功耗预测模型

针对双轴旋耕机结构参数复杂、功耗高，受耕作时节限制，难以用田间试验的方法进行减阻降耗研究的问题。基于离散元法，构建双轴旋耕-秸秆-土壤耕作模型，研究了双轴配置参数对功耗的影响，通过响应面试验分析，建立了功耗的数学预测模型。模型优化的结果表明，当前后刀轴回转半径均为195mm，后轴相对于前轴垂直距离为99.8mm，前后轴回转圆水平距离为100.6mm，获得的功耗最小为9.018kW。为了验证功耗模型的准确性，在固定工作参数下，进行了原尺度整机仿真试验和田间试验。试验结果表明：真实原尺度旋耕机的田间试验功耗与整机仿真值误差均值为9.5%，范围为5.8%~13.4%，结合响应面分析说明功耗数学预测模型较为准确，表明旋耕机刀组在缩放过程中误差变化较小，模型能够准确反映双轴配置参数对双轴旋耕机在稻茬田地作业功耗的影响。     

直线翼垂直轴风力机静态流场数值模拟与可视化试验

为研究翼型对直线翼垂直轴风力机启动特性的影响,选取了厚度相似的正装非对称翼型S809与通用对称翼型NACA0018进行两叶片垂直轴风力机的对比研究.首先,运用数值模拟的手段得到采用2种翼型风力机的周期静态力矩曲线,取得二者力矩差异较大的特定方位角,并且进一步获得特定方位角下的涡量图和矢量图.然后通过可视化试验得到叶片周围流场矢量图,并将其用来验证模拟结果的准确性.继而结合涡量图和矢量图,对2种风力机叶片周围的旋涡和流动变化情况进行分析.计算结果表明:2种翼型的力矩曲线随方位角变化规律一致,NACA0018翼型的启动性要好于正装S809翼型;叶片尾流的旋涡使流场变得不稳定,造成能量损失;2种翼型叶片尾流均有不同程度的旋涡产生,使流场变得不稳定,相比NACA0018翼型,正装S809翼型叶片后部的剪切流动更强,产生的旋涡更近,对叶片启动性的影响也更大.     

The impact of maternal overnutrition and obesity on hypothalamic-pituitary-adrenal axis response of offspring to stress

We evaluated the effect of maternal obesity before and throughout gestation on offspring hypothalamic-pituitary-adrenal axis function. Multiparous Rambouillet by Columbia crossbred ewes were fed either 100% of National Research Council (NRC) recommendations (control, C) or 150% of NRC recommendations (obese, OB) from 60 d before mating until lambing. Ten lambs born to OB ewes (five males and five females), and eight lambs born to C ewes (three male and five female) were studied. From delivery to weaning lambs were maintained with their mothers, who were all fed 100% NRC recommendations. After weaning, all lambs were group housed and fed the same diet to meet NRC requirements. At 19 mo of age lambs were placed in individual pens and fed a pelletized diet to meet maintenance requirements. Jugular vein catheters were placed and 2 d later lambs received an intravenous (i.v.) adrenocorticotropic hormone (ACTH) challenge followed by an i.v. corticotropin-releasing hormone (CRH)/arginine vasopressin (AVP) challenge 1 d later. Thirty d later offspring were again catheterized and placed into metabolism crates for 2 d before receiving an isolation stress test. ACTH and cortisol responses to the isolation stress test and CRH/AVP challenge and cortisol responses to ACTH challenge were determined. Cortisol was quantified via radioimmunoassay and ACTH was quantified using an Immulite 1000; both were analyzed using repeated measures using the MIXED procedure of SAS. Offspring from OB ewes had elevated basal plasma ACTH and cortisol compared with C offspring before all three challenges (P < 0.05). Offspring from OB mothers tended (P = 0.06) to have a greater ACTH response after an i.v. CRH/AVP injection than offspring from C mothers (12,340 ± 1,430 vs 8,170 ± 1,570 area under the curve, respectively). Cortisol response to the CRH/AVP and ACTH challenges was not influenced by maternal nutrition (P = 0.46) and averaged 4.77 ± 0.2 μg/dL and 1.94 ± 0.01 μg/dL, respectively. The ACTH response following the isolation stress test was also similar (P = 0.82) for OB and C offspring (147 ± 20 pg/mL), and cortisol response during the isolation stress test was similar between C and OB offspring (P = 0.64, 5.25 ± 0.3 μg/dL). These findings suggest that maternal obesity before and during gestation does not affect stress responses by the offspring, but has an impact on hypothalamic-pituitary-adrenal sensitivity. The lack of differences in cortisol release under the influence of difference concentrations of ACTH during the CRH/AVP challenge could indicate adrenal dysfunction in OB offspring.     

NDV对雏鸵鸟HPA轴的影响

以45日龄雏鸵鸟为试验动物,分正常组和攻毒组,利用RIA技术和TUNEL技术,探讨新城疫病毒（NDV）对雏鸵鸟HPA轴的影响。结果表明,雏鸵鸟感染NDV,HPA轴内细胞凋亡数量在病毒感染期间明显高于对照组,提示NDV能诱导雏鸵鸟HPA轴系统发生细胞凋亡;在病毒接种后1d,肾上腺内可检测到大量凋亡细胞,接种5d后凋亡数量显著增加（P〈0.05）,之后凋亡呈下降趋势,肾上腺内细胞凋亡的动态变化反映了雏鸵鸟HPA轴对ND病变的适应和调节。雏鸵鸟感染NDV,血清ACTH水平于NDV接种后1d开始上升,至5d达到峰值（P〈0.01）,之后有所下降,渐趋于正常;血清Cor水平于病毒接种后1d开始下降,至7d有所回升,9d渐趋于正常水平,表明NDV接种后雏鸵鸟血清ACTH和Cor水平的变化与其HPA轴功能的损伤及恢复密切相关。     

数控裁板锯切削主轴的可靠性分析

应用应力-强度干涉理论，分析了应力与强度概率密度函数为正态分布时轴的可靠性。考虑轴在扭矩及弯矩的复合作用下对其可靠性的影响，对数控裁板锯切削主轴进行了可靠性分析。通过实例设计结果的分析比较，说明了可靠性设计的可行性与实用性。     

基于多重激励的悬臂式多级离心泵轴心轨迹研究

针对悬臂式多级离心泵易出现陀螺效应,造成转子失稳与泵机组振动等问题,根据理论公式计算所得的密封流体激励力、泵腔流体激振力和附加质量代入有限元模型进行仿真计算,得到悬臂式多级离心泵的轴心轨迹图,并分别与未加载3种激励力、只加载密封流体激励力与添加密封和泵腔流体激振力的计算结果进行对比分析,最后利用Bently 408型便携式数据采集系统对轴心轨迹进行试验,对仿真进行验证。研究结果表明:加载叶轮口环密封力能够提高转子系统的稳定性,并能有效降低径向位移幅值;泵腔中流体激振力增加了转子系统的交叉刚度,导致振幅增加;相比于密封流体激励力和泵腔流体作用力,流体附加质量对悬臂式转子系统的瞬态响应的影响更为显著。