断奶日龄对仔猪生长的影响

仔猪的生长受机体神经-内分泌调节中枢的控制,其中下丘脑-垂体-肝脏轴(简称生长轴)对仔猪的生长发育影响最大。目前国内外关于不同断奶日龄对仔猪生长影响的报道较多,结果不尽一致,较为统一的结果显示,断奶日龄显著影响仔猪早期的日增重、日采食量和相对生长速率等生长指标,且断奶日龄越早,这些指标于断奶后下降的幅度越大。至42日龄以后,不同断奶日龄仔猪日增重、日采食量、体重以及相对生长速率等指标均无显著差异。然而,不同断奶日龄影响仔猪早期生长的分子机理目前尚不清楚,开展相关研究对指导不同断奶日龄仔猪确定合理的营养对策、科学确定仔猪断奶时间等均有重大理论意义。     

顺德新城区绿轴公园规划

文章以顺德新城区中心片区绿轴公园规划设计为例,强调城市商务中心区公园须充分绿化,为城市公共开敞空间提供绿色走廊,形成城市中的森林     

基于运动捕获数据的玉米叶片静力应变试验研究

为了研究玉米叶片在不同应力情况下的叶脉的形变情况,进而分析了叶脉骨架的生物力学及运动学特性,以叶尖直立展开期和定型期的玉米叶片为研究对象,提出了一种基于准确运动捕获数据的应力—应变试验方案。试验测试了主脉在不同静态荷载下的形变情况,并从宏观力学层面分析了主脉形变程度随距基部距离的变化趋势。结果表明:处于叶尖直立展开期和定型期的玉米叶片,其主脉上各点随着距基部距离不同表现出不同的生物力学特性,且叶脉垂直最高处的形变程度最大。该研究为应用运动捕获技术获取农学试验数据做出了初步探索。     

直立中央领导干树形条件下幼年苹果树体生长特性的研究

 在直立中央领导干树形条件下 ,M7、MM10 6、M 2 6中间砧幼年苹果树中心干生长速度快 ,4年生树高达到 2 .7～ 3.6m。中心干上抽生的侧枝数量多 ,红富士、王林、新红星和乔纳金 4个品种在 4年生时分别在 2 0～ 30 .5个之间 ,且主要在 2年生或者 2年生和 1年生中心干段上抽生侧生分枝。 4年生树相指标能满足生产上早果丰产的需要 :单株枝量大 ,乔纳金为 6 31个 ,红富士和王林 4 80个左右 ,新红星 312个 ;短枝比率高 ,红富士短枝占总枝量的 6 1% ,乔纳金和王林分别为 71%和 74 % ,新红星 81% ;侧生分枝角度开张 ,在 4 3°～ 6 9°之间 ;中心干及侧生分枝的生长势能够很快趋向缓和 ,在不采用任何人工控制生长措施的条件下 ,定植后的第 4年 ,主干的延迟生长量显著大幅度减弱 ,侧生分枝生长量在抽生的第 3年甚至是第 2年也显著地减小。     

Swine gut microbiota and its interaction with host nutrient metabolism

Gut microbiota is generally recognized to play a crucial role in maintaining host health and metabolism. The correlation among gut microbiota, glycolipid metabolism, and metabolic diseases has been well reviewed in humans. However, the interplay between gut microbiota and host metabolism in swine remains incompletely understood. Given the limitation in conducting human experiments and the high similarity between swine and humans in terms of anatomy, physiology, polyphagy, habits, and metabolism and in terms of the composition of gut microbiota, there is a pressing need to summarize the knowledge gained regarding swine gut microbiota, its interplay with host metabolism, and the underlying mechanisms. This review aimed to outline the bidirectional regulation between gut microbiota and nutrient metabolism in swine and to emphasize the action mechanisms underlying the complex microbiome–host crosstalk via the gut microbiota–gut–brain axis. Moreover, it highlights the new advances in knowledge of the diurnal rhythmicity of gut microbiota. A better understanding of these aspects can not only shed light on healthy and efficient pork production but also promote our knowledge on the associations between gut microbiota and the microbiome–host crosstalk mechanism. More importantly, knowledge on microbiota, host health and metabolism facilitates the development of a precise intervention therapy targeting the gut microbiota.     

适用于蔗渣进料的螺旋轴设计计算

较系统的论述了适于蔗渣进料用的螺旋轴几何参数的设计与计算,为解决早期制造的热磨机出现难进料及效率低的问题提供理论依据。     

播娘蒿幼蕾和花序轴的组织培养和再生植株研究

播娘蒿幼小花蕾在附加有１５ｍｇ／ＬＮＡＡ、０５ｍｇ／Ｌ６－ＢＡ和０１ｍｇ／ＬＫＴ的ＭＳ培养基中，培养两周即形成０５ｃｍ２大小的愈伤组织块，出愈率达８３％。继续培养两周转至附加有２ｍｇ／Ｌ６－ＢＡ、０５ｍｇ／ＬＫＴ和０２ｍｇ／ＬＮＡＡ的ＭＳ分化培养基上，２～３周后出现绿色芽点，继续培养２周即可得到分化小芽。播娘蒿花序轴在附加有２～６ｍｇ／Ｌ６－ＢＡ、０５ｍｇ／ＬＮＡＡ的ＭＳ培养基中，培养５～６周也都能分化出芽，但最佳培养基为４ｍｇ／Ｌ６－ＢＡ、０５ｍｇ／ＬＮＡＡ。分化小芽转至附加０５ｍｇ／ＬＮＡＡ或０５ｍｇ／ＬＩＢＡ的１／２ＭＳ生根培养基上培养２～３周均能形成完整植株。     

中间轴两端叉面夹角对万向铰链传动比的影响

应用球矢量函数研究双万向铰链机构的运动,推出传动比、传动比误差的计算公式及等速传动的条件,借助Matlab软件形象地分析了中间轴两端叉面夹角对传动比的影响,分析方法和结果对工程技术人员设计、制造、装配及调试双万向铰链机构具有指导意义。     

The immediate effects of weaning stress on the hypothalamus‐pituitary‐adrenal alteration of newly weaned piglets

This study was conducted to examine the effects of weaning stress on gene expression of specific markers in hypothalamus‐pituitary‐adrenal (HPA) axis and neuronal activity in the newly weaned piglets. Twelve 28‐days‐old, newly weaned crossbred (Landrace × Yorkshire × Duroc) male piglets from 6 l (2 piglets/l) were randomly categorized into two groups: (a) weaning stress: piglets were separated from their dams, relocated and mixed with the unacquainted domestic piglets for 2 hr (stress, n = 6); (b) no‐stress: piglets stayed with their dams in the farrowing house (NS; n = 6). After weaning stress, all piglets were electrically euthanized and the blood samples/HPA tissues were collected for subsequent analysis, including plasma cortisol and mRNA expression of c‐fos, c‐jun, corticotropin‐releasing hormone (CRH), CRH receptor 1 (CRHR‐1) and adrenocorticotropin hormone receptor (MC2R). Results: Weaning stress significantly (p < 0.05) increased the plasma cortisol level and suppressed the expression of c‐fos and CRH in hypothalamus. In addition, weaning stress enhanced the mRNA abundance of c‐jun and CRHR‐1 in the pituitary gland. No significant differences in the gene expression of MC2R and CRHR‐1 were observed in the adrenal gland between treatment groups. Taken together, HPA involved in weaning stress and CRHR‐1 and c‐jun could be potential markers to evaluate the activation of HPA axis.     

基于滑移网格的垂直轴风力机非定常数值模拟

采用滑移网格技术对直叶片垂直轴风力机进行了非定常数值模拟,得到尾流速度、特定过流断面的速度分布规律,并与经典的多流管理论计算出的尾流速度、特定过流断面速度进行了对比,数值模拟结果与理论计算值吻合较好.结果表明,采用滑移网格技术对直叶片垂直轴风力机进行非定常的数值模拟能够较好地反映流场特性.