动态载荷下基于声发射技术的杨木破坏过程检测

利用声发射检测和力学试验相结合的方法,研究山杨木材在动态载荷下的声发射演变过程;结合木材粘弹性特点,通过声发射参数分析研究在不同受力阶段木材的声发射特点.结果表明:1)声发射信号幅值不连续,是跃迁的;材料断裂前声发射信号的幅值和能量比断裂后小,在断裂点对应声发射信号幅值和能量的局部极大值.2)随时间和载荷的变化,声发射累计撞击数和累计能量增加快慢可以体现杨木在受力条件下的完全弹性、弹性为主的弹塑性共存、塑性为主的弹塑性共存3种状态.3)声发射率和幅值参数可以预测材料纤维开始断裂进入危险期的第一"临界点"和材料大量纤维断裂进入严重危险期的第二"临界点",如果继续加载材料将会破坏断裂.     

Approaches to Configuration Determinations of Flexible Marine Natural Products: Advances and Prospects

Flexible marine natural products (MNPs), such as eribulin and bryostatin, play an important role in the development of modern marine drugs. However, due to the multiple chiral centers and geometrical uncertainty of flexible systems, configuration determinations of flexible MNPs face great challenges, which, in turn, have led to obstacles in druggability research. To resolve this issue, the comprehensive use of multiple methods is necessary. Additionally, configuration assignment methods, such as X-ray single-crystal diffraction (crystalline derivatives, crystallization chaperones, and crystalline sponges), NMR-based methods (JBCA and Mosher’s method), circular dichroism-based methods (ECCD and ICD), quantum computational chemistry-based methods (NMR calculations, ECD calculations, and VCD calculations), and chemical transformation-based methods should be summarized. This paper reviews the basic principles, characteristics, and applicability of the methods mentioned above as well as application examples to broaden the research and applications of these methods and to provide a reference for the configuration determinations of flexible MNPs.     

基于NbS的北京市乔木林固碳能力分析

[目的]乔木林生物质碳汇是影响森林碳汇的重要组成部分,是一种自然的气候解决方案,在全球气候变化大背景下,森林的固碳潜力一直被广泛关注,本文以北京市为例,分析不同的林业活动对乔木碳储量的影响.[方法]采用北京市森林资源设计调查数据,利用IPCC材积源-生物量法估算北京市乔木林碳储量,分析了2009-2014年北京市在森林...     

Taxonomic and Bioactivity Characterizations of Mameliella alba Strain LZ-28 Isolated from Highly Toxic Marine Dinoflagellate Alexandrium catenella LZT09

Microalgae host varied microbial consortium harboring cross-kingdom interactions with fundamental ecological significance in aquatic ecosystems. Revealing the complex biofunctions of the cultivable bacteria of phycosphere microbiota is one vital basis for deeply understanding the mechanisms governing these dynamic associations. In this study, a new light-yellow pigmented bacterial strain LZ-28 was isolated from the highly-toxic and harmful algal bloom-forming dinoflagellate Alexandrium catenella LZT09. Collective phenotypic and genotypic profiles were obtained to confidently identify this strain as a new Mameliella alba member. Comparative genomic analysis showed that strain LZ-28 shared highly similar functional features with other four marine algae-derived M. alba strains in spite of their distinctive isolation sources. Based on the bioactivity assaying, the mutual growth-promoting effects between bacterial strain LZ-28 and algal strain LZT09 were observed. After the culture conditions were optimized, strain LZ-28 demonstrated an extraordinary production ability for its bioflocculanting exopolysaccharides (EPS). Moreover, the portions of two monosaccharides glucose and fucose of the EPS were found to positively contribute to the bioflocculanting capacity. Therefore, the present study sheds light on the similar genomic features among the selected M. alba strains, and it also reveals the potential pharmaceutical, environmental and biotechnological implications of active EPS produced by this new Mameliella alba strain LZ-28 recovered from toxic bloom-forming marine dinoflagellate.     

CO2、温度对葡萄群体光合作用的影响

采用人工气候室作物群体光合作用测定分析体系研究了CO2、温度等环境因子对巨峰葡萄花期、膨大期群体总光合速率(Pgc)的影响。无论花期还是膨大期Pgc都随CO2浓度及温度升高呈线性增加;温度对巨峰葡萄群体光合作用影响明显,高温降低了初始光化学效率(αc),在低CO2浓度下提高了巨峰葡萄群体的最大光合速率。初步确定了CO2浓度为400mmol·L-1时,不同光照条件下获得最大群体光合速率的适宜温度。     

医用农业发展初探

探讨了医用农业的概念、基本涵义和主要类型,在考察国外医用农业发展的基础上,展示了医用农业广阔的发展前景。初步研判提出,医用农业是现代农业发展的新趋势,发展医用农业是我国特别是沿海发达地区现代农业发展的必然抉择。     

粗纤维在母猪饲粮中的应用

粗纤维是母猪营养的未来,也是今后母猪营养的发展方向。文章着重介绍母猪能利用粗纤维的原因及粗纤维对母猪的影响,为今后粗纤维在母猪饲粮中的利用提供科学指导。     

叶片布置方式对双吸离心泵径向力的影响

为研究叶片布置方式对双吸离心泵径向力的影响,在其他外部因素不变的情况下,对3种叶片布置方案的离心泵进行非定常模拟计算,结果表明:较对称布置方案,采用交错30°布置的叶片能够有效提高离心泵的扬程,采用交错15°布置的叶片对离心泵扬程具有消极影响.同时,采用交错布置方案会导致离心泵的效率下降;在设计工况下,与对称布置方案相...     

苹果采后加工碰撞损伤影响因素研究

针对苹果在清洗、分级和包装等采后加工过程中损伤率较高的问题,以红富士苹果为试验材料,利用自制的苹果跌落试验台,研究跌落高度、果实质量、碰撞材料对苹果碰撞损伤的影响.通过3因素3水平正交试验,分析试验因素对苹果碰撞损伤体积影响显著性;并通过试验确定苹果在2种碰撞材料下的碰撞损伤临界跌落高度.试验结果表明:影响苹果碰撞损伤...     

中国北方野生雄绒螯蟹成蟹可食率和生化成分分析

比较了2017年10月由我国绥芬河、图们江和辽河采集的质量为80～160 g的野生雄绒螯蟹成蟹的组织系数、总可食率、可食组织中一般化学组成及脂肪酸组成.试验结果显示:(1)3个种群雄体性腺指数、肝胰腺指数和出肉率差异显著,但3个种群总可食率无显著差异(P>0.05).(2)就性腺而言,图们江种群水分含量最高,绥芬河种群...