关于入侵物种三联密码子的基因签名

寡核苷酸的频率分布具有物种特性,可看作是一种基因签名.本文计算一些入侵植物中部分DNA序列的三联密码子出现频率,并将此频率分布用二维平面图和一维柱状图表示,作为物种的基因签名.通过对不同入侵物种基因签名的分析比较,发现入侵物种的DNA序列非随机,基因签名具有物种特性,且物种越近,签名越相似.同时签名有局部相似性的,物种在某方面也具相似性.即签名可在一定程度上表征物种的分类和进化关系.另外,鉴于生物入侵过程实际上是快速进化过程,采用人工基因突变的方法将原始DNA序列转化为突变序列,并将原始序列和突变后序列的基因签名作比较,发现DNA序列三联密码子出现频率具有分布差异,这些差异可导致对应蛋白质结构和功能的改变,进而改变物种特性.     

Properties of Natural Fibers Separated from Chromolaena odorata and Mikania micrantha

This paper reports the possibility of separating natural fibers from two invasive alien plants Chromolaena odorata and Mikania micrantha. These two are considered as high-risk species on the basis their invasiveness and being a menace to the natural biodiversity of Kerala, India. Water retting and alkali extraction methods were used for the separation of stem fibers. Fibers obtained showed similar properties to currently used common fibers. Based on morphometric measurements and derived values, such as slenderness ratio, flexibility ratio, and Runkel ratio, these fibers are expected to be suitable for industrial purposes.     

Comparison of Taxon‐Specific and Taxon‐Generic Risk Screening Tools to Identify Potentially Invasive Non‐native Fishes in the River Neretva Catchment (Bosnia and Herzegovina and Croatia)

The Freshwater Fish Invasiveness Screening Kit (FISK) v2 and Aquatic Species Invasiveness Screening Kit (AS‐ISK) risk identification screening tools were used to assess the invasiveness potential of 24 non‐native (NNS) freshwater fish species in the River Neretva catchment (Bosnia and Herzegovina and Croatia), a risk assessment (RA) area that is an important Mediterranean hotspot for fish endemism. The two assessors assigned similar scores for the invasiveness potential of the NN fishes, and both screening tools successfully distinguished invasive from non‐invasive species. Mean calibrated threshold scores were 10.25 for FISK and 10.00 for AS‐ISK, with the latter increasing to 12.62 when questions that assess the likely impact of predicted future climate conditions on the RA were taken into consideration. These relatively low threshold values are characteristic of areas with an elevated number of translocated species and suggest that NN fishes pose a considerable threat to native species and ecosystems. FISK ranked 50.0–62.6% of the species as being of ‘high risk’ compared with 58.4–59.3% using AS‐ISK. The highest scores (‘very high risk’) were attributed to gibel carp Carassius gibelio (Bloch, 1782) and pikeperch Sander lucioperca (Linnaeus, 1758). The generic screening tool for aquatic species (AS‐ISK) provided similar risk rankings to its predecessor, FISK, as regards invasiveness potential. For this reason, it is likely to be an effective tool for evaluating the potential invasion risk of NNS freshwater fishes for other RA areas in the Balkans. Copyright © 2017 John Wiley & Sons, Ltd.     

大长径比铝合金异形件精密旋压成形工艺研究

通过工艺试验及组织性能分析,研究了变形温度、道次和减薄率、进给比对大长径比铝合金异形件旋压成形的影响,优化的特征旋压温度为370~420 ℃、变形道次为10~12道次、道次减薄率为20~25 %、总减薄率为35~50 %、普旋进给比为2.0~2.5 mm/r、强旋进给比为1.3~1.8 mm/r。采用上述工艺实现了大长径比异形旋压件经历1次装卡由板材直接成形,大幅提升了生产效率,同时满足构件“控形”和“控性”要求,其壁厚差≤0.2 mm,内型面与理论型面单边间隙≤0.1 mm,旋压变形后抗拉强度和延伸率基本不变、而屈服强度提高10.1 %。     

离子掺杂钇铁石榴石磁光材料研究进展

综述了钇铁石榴石型磁光材料的研究进展,以及通过离子掺杂提高单晶和薄膜材料的比法拉第旋转角、改善材料温度稳定性以及近年来受到重视并有望在磁光器件中得到广泛应用的低成本钇铁石榴石纳米晶/有机分散介质复合薄膜材料的研究进展与存在的问题,概述了目前实际使用中的磁光法拉第转子材料的应用情况,并展望了高性能磁光材料的发展。     

小麦异源细胞质遗传特点的研究

本文以普通小麦中国春细胞核置换到小麦属和山羊草属不同细胞质的同核异质稳定置换系,以及普通小麦不同品种的细胞核置换到卵圆山羊草细胞质的同质异核稳定置换系为材料,研究了异源细胞质在生育期、剑叶光合特性、电导率、花粉育性及主要农艺性状等方面的遗传特点,分析了异源细胞质遗传效应的差异性和稳定性,讨论了核质杂种的核质互作关系以及异源细胞质的遗传机制,并指出了小麦异源细胞质遗传效应的应用前景.