Neuroprotective cadinane sesquiterpenes from the resinous exudates of Commiphora myrrha

Three new cadinane sesquiterpenes, commiterpenes A−C (1−3), were isolated from the resinous exudates of Commiphora myrrha. Their structures and relative configurations were elucidated by spectroscopic methods (IR, ESIMS, HRESIMS, 1D and 2D NMR). All the isolated sesquiterpenes showed neuroprotective effects against MPP⁺-induced neuronal cell death in SH-SY5Y cells.     

Morphological plasticity and phosphorus uptake mechanisms of hybrid <Emphasis Type="Italic">Eucalyptus</Emphasis> roots under spatially heterogeneous phosphorus stress

In this study, we subjected the root systems of eight Eucalyptus hybrids currently cultivated in southern China to heterogeneous phosphorus stress to provide a scientific basis for the selection of a highly phosphorus-efficient Eucalyptus variety. When the ability of these hybrids to locate phosphorus under different experimental conditions (phosphorus supply in a homogeneous or heterogeneous manner vs. no phosphorus supply) was compared, the main growth characteristics of Eucalyptus, such as plant height, diameter, dry mass, and phosphorus content, significantly improved when the phosphorus supply was increased from no phosphorus or heterogeneous phosphorus (half of the phosphorus amount) to homogeneous phosphorus. Across these three conditions, the growth traits of different Eucalyptus hybrids differed significantly, indicating different adaptabilities of the hybrids to various phosphorus conditions. The growth traits of the aboveground tissues of Eucalyptus under different phosphorus conditions were largely influenced by the morphology of the underground root system. In addition, the root morphology of Eucalyptus under heterogeneous phosphorus treatment suggested that there were two mechanisms for locating nutrients. Eucalyptus hybrids such as Urophylla 3229, Grandis 9, Guanglin 3, 201-2, and Dunn produced more roots proximal to the phosphorus supply; the other hybrids, Urophylla 3216, Grandis 5, and Guanglin 9, relied mainly on the growth of roots opposite the phosphorus supply to obtain adequate nutrients for growth. With these two strategies, a wide range of nutrients was obtained, root distribution was greater, more soil volume was covered, the contact area of the roots with soil phosphorus was increased, and the uptake of phosphorus by the root system was increased. These results demonstrate that Eucalyptus relies on changes to morphological characteristics of the root system to increase accessibility to phosphorus resources.     

林业产品价格竞争的数学模型

应用微分法建立林业产品价格竞争的数学模型,并提出在激烈的价格竞争中企业的应对策略。     

继代培养基再利用研究

利用组织培养法繁育三倍体山杨继代丛生无根苗过程中,为降低育苗成本,利用回收转换后废弃的继代培养基,进行再利用试验研究,分别加入了原继代培养基１０％,２０％,３０％,４０％,５０％的母液,不加琼脂和糖,用原继代培养基做对照。     

海南省椰心叶甲蔓延成因分析

海南省椰心叶甲蔓延的主要原因为：地处热带地区、棕榈科植物种类丰富、椰心叶甲繁殖速度快、成活期长、天敌昆虫较少、微环境适宜、防治难;加强检疫,化学防治和生物防治相结合,能有效防止和控制椰心叶甲的为害和蔓延。     

山地杨栽植技术研究

为探索山区杨树造林的最佳方式,提高造林成效,2002年3月在建始县高坪镇采用带根苗造林、截干苗造林、插干苗造林3种不同的栽植方式对MD19等10个无性系进行对比试验。结果表明:采用带根苗造林的效果最好,造林后能迅速成林,成活率、保存率均高,生长最好;无性系中以MD19、MD110生长最快,在生产中可以大面积地推广应用。     

Natural convection heat transfer in the air layer of insulating glass

The numerical simulation with FLUENT software is addressed for the natural convection heat transfer under the conditions of different air layer thickness with 6 mm,9 mm,12 mm,14 mm and 16 mm. The heat transfer rate is compared with that by heat conduction. Gas types, Rayleigh number (Ra),the relative thickness of air layer,δ/H,and the surface (ΔT) are main factors for natural convection heat transfer. The natural convection heat transfer could be approximately regarded as the pure heat conduction in the conditions of above air layer thickness. The heat transfer coefficient of the insulating glass with simulation is approximate to that with empirical calculation.     

分子标记技术在蔬菜作物品种鉴定与纯度检测中的应用

品种鉴定与遗传纯度检测是蔬菜作物种子品质检验极为重要内容。本文综述了以蛋白质、DNA为基础的分子标记,如蛋白质与同工酶、RELP、RAPD、SSR、ISSR等分析技术应用于蔬菜种子检测的基本原理与进展。利用标记分析技术成功进行F1种子纯度检测的关键是亲本与杂交种间稳定差异位点的获得。已获得的重要园艺性状紧密连锁的遗传标记将有利于F1种子纯度鉴定。由于分子标记客观、稳定、快速、高效,这些技术将在今后种子检测中起到重要作用。