Effect of dietary physically effective fiber on ruminal fermentation and the fatty acid profile of milk in dairy goats

The objective of this experiment was to characterize the relationship among rumen fermentation variables, milk fatty acid profile, and dietary physically effective neutral detergent fiber (peNDF) content in a study that controlled for the potential confounding effects of dissimilar dry matter intake among treatments. Ten multiparous Xinong Saanen dairy goats were divided into 2 groups with 2 ruminally cannulated goats per group. Goats in each group were assigned to 1 of 2 dietary treatments (high and low peNDF) according to a 2 × 2 crossover design with 2 periods. The peNDF content of alfalfa hay (proportion of neutral detergent fiber retained on an 8.0-mm screen) was 42.1% for the high-peNDF and 14.5% for the low-peNDF group. To ensure similar dry matter intake, each morning the amount of alfalfa hay consumed on the prior day by the high-peNDF group was determined (amount offered minus morning refusals), and this was the amount of hay offered to the low-peNDF group that day. Each adaptation period consisted of 21 d, followed by a 9-d sampling period. Dry matter intake and milk production and composition were similar between treatments. Milk energy efficiency increased with low dietary peNDF. Duration of pH below 5.60 was longer for goats fed the low-peNDF ration compared with the high-peNDF ration (4.08 vs. 0.41 h/d); however, mean rumen pH (6.05 vs. 6.13) was not different between treatments. Reducing dietary peNDF increased rumen total volatile fatty acids (114.6 vs. 95.1 mM) and decreased chewing time (404 vs. 673 min/d), but did not affect the ratios of acetate, propionate, and butyrate. The relative abundance of Fibrobacter succinogenes and Ruminococcus flavefaciens increased with reduced dietary peNDF, but Ruminococcus albus proportions were not influenced by treatment. Reducing dietary peNDF decreased the proportion of iso C14:0, iso C15:0, and trans-11 C18:1 in milk fat, whereas the iso C17:0 and trans-10 C18:1 increased. This study demonstrated that low dietary peNDF in dairy goats increases rumen volatile fatty acids, reduces chewing time, and is correlated to the amount of F. succinogenes and R. flavefaciens.     

控制轧制对GCr15盘条冷拉工艺的影响

对高速棒线材连轧机与复二重轧机轧制的ＧＣｒ１５盘条进行了组织、晶粒度、性能及盘条球化退火、拉丝工艺等方面对比表明：控制轧制对改善ＧＣｒ１５钢盘条组织、性能及简化退火工艺,提高拉丝总压缩率有明显效果。     

pH-triggered poly(ethylene glycol) nanogels prepared through orthoester linkages as potential drug carriers

The new acid-labile poly(ethylene glycol) (PEG) nanogels were prepared by copolymerization of a new crosslinking agent containing orthoester groups (OEAM) and methoxypolyethylene glycol acrylate (MPEGAC). DOX was loaded into PEG nanogels with a loading content of 18.2%, which was highly desirable for targeted cancer therapy without premature drug release in neutral environment. The cellular uptake and cytotoxicity of DOX-loaded PEG nanogels were measured using SH-SY5Y and HepG2 cells. Tumor penetration and antitumor activity were investigated using SH-SY5Y tumor-like spheroids. All results demonstrate that the pH-sensitive PEG nanogels may be used as potential drug carriers for chemotherapy.     

微乳液法在超细炸药制备方面的应用概述

以超细炸药的制备为主线,对微乳液法在炸药超细颗粒的制备进行了概述。明确了微乳液的定义以及其和纳米乳液的区别;对微乳液法制备超细炸药的机理、细化过程中的影响因素以及此方法制备出超细炸药的性能进行了归纳总结,并指出了今后研究工作中应注意的一些问题和研究重点。     

钢筋砼及预应力砼结构设计方法的新进展——略论新修订的《混凝土结构设计规范》特点

本文简要地介绍了新修订的《混凝土结构设计规范》的特点,着重于介绍对现行规范所作的重要修改和增添部分,其中包括以概率理论为基础的极限状态设计方法、建立构件正截面强度计算体系、复合力作用下的结构构件截面强度计算、正常使用极限状态的验算及钢筋的锚固设计等,使读者对新修订的规范有一个概括的了解。     

城市地下空间网络化拓建相关研究进展

随着我国城市地下空间的快速发展,规划落后于建设实践的矛盾日益突显,地下空间的碎片化开发及不合理规划带来了诸多问题。基于既有浅层地下空间建设网络化地下空间的需求导向,提出了“规划设计先天不足、拓建开发后天弥补”的浅层地下空间拓建思路。通过地下空间拓建案例统计分析,提出了网络化地下空间、地下空间拓建等相关概念,以及拓建方式的5种基本类型和18种亚级类型。在地下空间拓建扰动传导路径及内在工作机制分析基础上,提出了城市地下空间拓建扰动分级评价体系,建立了不同拓建方式之间的联系。基于不同拓建方式的施工关键技术研究和典型案例解析,提出了城市地下空间网络化拓建技术将向透视地下、高效装备、装配结构和智能建造方向发展的未来趋势。研究成果可为未来城市地下空间高效、规范拓建提供发展思路和发展模式,促进城市地下空间网络化发展。     

城市网络化地下空间品质提升及评价指标体系

随着我国社会经济快速发展,城市网络化地下空间对于缓解城市人口、资源及环境间的矛盾具有重要意义。然而受制于周边建(构)筑物、复杂地质水文条件影响,地下空间在空间网络构建、艺术处理手法赋予方面具有先天不足,特别是由于地下空间与地面空间的天然隔绝,易产生压抑和封闭的感觉,导致使用者情感上浮现“陌生”和“趋离”的倾向。因此,地下空间建设需具有人性化特点和场所精神的设计理念,赋予地下空间使用者于“归属感”和“认同感”,通过对地下空间的综合性开发和科学合理规划,来提升地下空间建设及使用品质。本文以构建高品质地下空间为目标,基于“以人为本”理念,从人为感知出发,围绕人对“安全、高效、舒适、绿色”等四方面的需求与体验,提出以人为本的地下空间品质评价指标体系,提炼网络地下空间品质优化规划设计要素,为实现地下空间规划品质由质化评价向量化评价过渡及后续的地下空间开发的品质优化和提升提供技术支撑。     

带电检测技术在750kV GIS设备中的一例典型应用

电力设备带电检测是发现设备潜伏性缺陷的有效方法,是保障电力设备安全、稳定运行的重要手段。介绍了GIS设备内部常见缺陷、GIS局部放电检测技术原理,通过一起局部放电检测技术在750 kV GIS设备上的应用,成功发现了设备内部存在的缺陷并对其进行定位,最终找到了缺陷原因并进行了现场处理。通过介绍表明,对GIS设备进行带电检测,能够在缺陷初期及时发现设备内部存在的异常,并根据检测结果指导开展设备检修工作。     

凡口铅锌矿矿柱回采稳定性数值模拟研究

通过运用加拿大rocscience研究所研发的二维有限元数值模拟软件Phase2对凡口铅锌矿较典型的N4-5采场逐步进行了动态模拟分析。通过分析,准确模拟了采场回采过程中的应力分布及位移变化情况,为优化采场结构参数和指导地压控制提供了可靠的依据。