灌木枝系结构与积沙效能野外观测

通过对油蒿(Artemisia ordosica)、沙蒿(A.desertorum)、梭梭(Haloxylon ammodendron)、花棒(Hedysarum scoparium)、白刺(Nitraria tangutorum)、红砂(Reaumuria soongorica)、沙拐枣(Calligonum mongolicum)和两种仿真灌木的各级枝数量的观测,分析比较了灌木枝系结构与其积沙量关系。结果显示:半球形的仿真灌木积沙量最大;灌木积沙量与其总体分枝率成反比,但不同形状的灌木积沙量取决于枝系结构。积沙量较大的梭形和半球体灌木是内密外疏,而坛状灌木的内外疏而中间密的积沙量较大。灌木积沙量与枝系结构复杂程度有密切联系,且随着总体分枝率和逐步分枝率变异系数增大而增大。

石羊河下游7种沙生灌木的构型比较

为了明确比较相同环境下不同灌木的构型特征,揭示其防风固沙机理,也为仿真模拟研究提供基础数据,该研究对石羊河下游的相同环境下,高度相似的梭梭(Haloxylon ammodendron)、油蒿(Artemisia ordosica)、沙蒿(A.arenaria)、花棒(Hedisarum scoparium)、沙拐枣(Calligonum mongolicum)、白刺(Nitraria tangutorum)、红砂(Reaumuria kaschgarica)7种灌木的分枝角度、枝长和分枝数等构型指标进行测量分析。结果表明:(1)7种灌木中有6种的平均分枝角度自冠层内部向外逐渐变大,枝序级可分为四级,除油蒿外,其余灌木的冠层外枝均较长。(2)分枝分维数以红砂最大,其次为梭梭和白刺,沙拐枣和花棒最小;除梭梭外,其余灌木的总体分枝率都小于1。(3)除沙拐枣外,其余灌木的侧影面积随高度增加而增加,达到最大值后又逐渐减少。研究认为,生长在相似环境的灌木形成了不同构型,红砂、白刺、油蒿和花棒可归为密生枝型灌木,梭梭、沙拐枣和沙蒿则可定为疏生枝型灌木。

Pathotype Structure of Magnaporthe grisea in the Fields of Chongyang and Yuan'an in Hubei Province,China

[Objective] This study aimed to explore the pathotype structure of Magnaporthe grisea in Chongyang and Yuan'an in Hubei Province,China.[Method] From the rice-growing fields of Chongyang and Yuan'an in Hubei Province where rice blast occurs frequently,60 isolates which were pathotyped against two sets of host differentials:Chinese host differentials and CO39 NILs,were obtained.Then,20 pathotypes with the six indica host differentials(CO39 NILs) were observed,while 13 pathotypes in four race groups were observed out of the same single spore isolates with Chinese host differentials which consists of three indica cultivars and four japonica cultivars.The diversity of the pathotypes of M.grisea populations tested by CO39 NILs was 2.54 and the pathotype 137.1 occurred at predominantly high frequency(21.67%).The diversity of physiological races of M.grisea populations tested by Chinese host differentials was 1.22 and the race group ZA occurred at predominantly high frequency(73.33%).The diversity of physiological races of M.grisea in Chongyang and Yuan'an were also calculated.Overall,the diversity of pathotypes of M.grisea in Yuan'an was higher than that in Chongyang with the two sets of the host differentials.[Conclusion] This study provided current information on the pathotype spectrum of M.grisea populations in the rice fields of Hubei Province to allow the formulation of viable strategies for blast resistance breeding programs in Hubei Province.

Dendrimers-merging biomimics and photoenergy conversion

Dendrimers are well-defined tree-like macromolecules possessing numerous chain ends emanating from a single core, which makes them attractive candidates for mimicking light-harvesting systems and hydrogenases. Photoinduced electron and energy transfers are main processes involved in light-harvesting and photocatalysis. In this review, the general concepts of design strategies and recent developments of photofunctional dendrimers in biomimics of light-harvesting systems and hydrogenases are discussed. The energy transfer and electron transfer processes in light-harvesting dendrimers and the effect of dendritic structures in photochemical hydrogen production are illustrated.

Fluctuation limits of strongly degenerate branching systems

Functional limit theorems for scaled occupation time fluctuations of a sequence of generalized branching particle systems in Rd with anisotropic space motions and strongly degenerated splitting abilities are studied in the cases of critical and intermediate dimensions. The results show that the limit processes are time-independent measure-valued Wiener processes with simple spatial structure.

A second-order nonlinear optical dendronized hyperbranched polymer containing isolation chromophores： achieving good optical nonlinearity and stability simultaneously

Large nonlinear optical(NLO) coefficient and good stability, two essential factors to evaluate second-order NLO materials, are difficult to be achieved in one molecule simultaneously. Herein, by utilizing the concept of "isolation chromophore", "isolation group" and dendritic structure, a dendritic molecule D-NS and a dendronized hyperbranched polymer DHP-NS are prepared to investigate their structure-property relationship. For the small dendritic molecule D-NS, it exhibits a high d33 value of 140 pm/V.But this value can be easily dropped when the temperature is higher than 50 °C, which extremely limits its real application. After introducing D-NS into a dendronized hyperbranched polymer chains, the obtained DHP-NS also shows a high d33 value of101 pm/V, but much better stability than D-NS. Even when its thin film was heated to 120 °C, no obvious decay can be observed in the d33 value of DHP-NS. This work demonstrates an effective strategy to realize both large NLO effect and good stability simultaneously.