松材线虫行为学研究进展

对松材线虫的侵入、松材线虫在树体内的运动与迁移、取食和繁殖等方面的行为学研究进展进行综述。松材线虫侵入寄主体内主要是随着松天牛取食进行的；而类脂含量降低后，松材线虫具有脱离松天牛而进入寄主的特性；挥发性物质尤其是β-香叶烯在松材线虫进入树体内起重要作用。温度、湿度、不饱和脂肪酸、树脂道、寄主生理状况等均影响到松材线虫的运动与迁移。松材线虫侵入树体后，大多滞留在树脂道，蜕皮变为成虫后再向其它部位迁移。蛹室中天牛释放的化学物质可吸引松材线早向蛹室迁移。松材线早在树体内主要以薄壁细胞为食，病树枯死后则以真菌等为食。温度和水分是影响松材线早繁殖行为的主要外界因子。松材线早的性引诱方式为相互引诱，但性信息素的化学特性尚等继续研究。     

松材线虫在抗性黑松体内移动及寄主水势变化

以接种松材线虫的1年生抗性黑松苗为实验材料,用感病黑松苗作对照来研究松材线虫在抗性黑松体内的移动及寄主水势变化.结果表明:接种初期,松材线虫在树体内的数量少,移动速度慢;在抗病黑松体内,线虫主要向下移动,且虫体数量明显少于在感病黑松体内的数量;在感病黑松体内线虫自接种点向上、下移动,且向下移动的速度和虫体数量明显大于向上的.随着时间的推移,线虫开始繁殖,扩散能力增强.水势测定结果显示,感、抗病黑松水势变化总趋势是先上升后下降再上升.     

松材线虫体内细菌对宿主繁殖和致病力的影响

为探讨松材线虫体内细菌在松材线虫病中的作用,对无菌松材线虫、体内细菌处理的松材线虫和野生型松材线虫的繁殖量和致病力进行了测定。结果表明:在非寄生条件下,无菌松材线虫的产卵量、卵孵化率和繁殖量显著高于携带细菌的松材线虫; 松材线虫体内寄生菌嗜麦芽窄食单孢菌NSPmBx03胞外代谢产物对松材线虫产卵量具有一定抑制作用。不同处理的松材线虫接种到3年生马尾松后,其繁殖量从高到低为野生型松材线虫>体内细菌处理的松材线虫>无菌松材线虫。对马尾松发病情况观察发现:接种野生型松材线虫的马尾松发病最早,病程最短; 次之为接种体内细菌处理的松材线虫; 最后是接种无菌松材线虫的处理。这表明嗜麦芽窄食单胞菌NSPmBx03对松材线虫在寄生和非寄生条件下繁殖的影响不同,对松材线虫致病力有一定增强作用。     

不同致病力线虫接种黑松后寄主体内组织病理学变化

分别用强、弱致病力松材线虫和无致病力拟松材线虫接种2年生黑松苗,发现不同致病力线虫在黑松苗体内的迁移特性不同,导致黑松苗产生的组织病理学变化也有差异.强致病力松材线虫扩散主要通过轴向树脂道在树体内上下扩散,通过径向树脂道在树体内向外扩散,并以此成为逾越形成层的通道,由于松属植物树脂道是遍布整个树体的一个"管网系统",所以线虫扩散速度快;弱致病力松材线虫扩散主要在皮层中,扩散速度慢,致病速度慢;无致病力拟松材线虫主要分布在皮层中,仅仅在少数皮层树脂道中发现线虫,而其对韧皮部、维管形成层细胞、木质部的射线细胞和树脂道周围的薄壁细胞未造成影响,也不能大量繁殖,因而对黑松不致病.无论是强致病力松材线虫还是弱致病力松材线虫接种后均未观察到线虫直接侵入松树形成层细胞,形成层细胞的死亡是一个渐进的过程,与线虫未到达的树脂道上皮细胞等薄壁细胞的死亡方式类似.     

不同线虫在黑松体内的扩展速度与致病性

分别用强、弱致病力松材线虫和无致病力拟松材线虫接种2年生黑松苗.观察结果表明:强致病力松材线虫在黑松体内扩散速度较快,4 d针叶开始发黄,7d松苗新梢开始萎蔫下垂,10 d松苗萎蔫,线虫在松苗体内大量繁殖,超过接种时的线虫数;弱致病力松材线虫在黑松体内扩散速度较慢,7 d针叶出现发黄的迹象,15 d新梢开始蒌蔫,25 d松苗整株萎蔫,线虫数量开始增加,超过接种时的线虫数;无致病力拟松材线虫接种后7 d仅在树梢分离到少量线虫,梢部部分针叶发黄,之后线虫基本未繁殖,25 d松苗体内已分离不到线虫,梢部针叶症状未加剧,松苗生长与对照类似.因此,黑松感染线虫后,是否发病与线虫能否在松苗体内存活有关,发病速度快慢与线虫在松苗体内扩散速度及能否大量繁殖有直接关系.     

松材线虫在松树体内扩散及其引起的寄主细胞反应研究进展

松材线虫病是松树最危险的病害之一，在世界上一些国家都有发生并且损失惨重。寄主松树感染松材线虫[Bursaphelenchus xylophilus （Steiner＆Buhrer）Nickle]40天后即可死亡。我国自1982年在南京中山陵风景区首次发现以来，到2000年底，因病枯死的松树达到2000多万株，直接经济损失25亿元，间接损失250亿元。松材线虫侵入寄主（主要是松树）后，在其体内迁移、分布及其引起的寄主内部细胞学、组织学的变化。病害发展过程与致病相关性。     

松材线虫萎蔫病病死木的空间分布型

应用频次分析方法研究了松材线虫萎蔫病病死木和林分中原有松树的空间分布型。松材线虫萎蔫病病死木在马尾松林内的分布为聚集分布,主要为波松－二项分布,林分内原有松树的分布为随机分布,说明松材线虫萎蔫病病死木的聚集分布不是由林分内原有松树的分布所引起。     

不同致病力线虫侵染后黑松的水势和根系活力的变化

分别用强、弱致病力松材线虫虫株和无致病力拟松材线虫虫株接种2年生黑松,观测接种后不同时间段黑松茎段水势和根系活力变化情况。结果表明：接种强、弱致病性松材线虫虫株后,在未表现出明显症状时,黑松水势都有一个降低然后回升的过程,但当树体内线虫开始大量繁殖、外部表现萎蔫症状时,黑松水势发生不可逆转的急速降低,松树死亡,强致病性松材线虫虫株比弱致病性松材线虫虫株导致黑松茎水势丧失速度快。接种无致病力拟松材线虫后,开始黑松水势下降,然后缓慢回升接近正常水势,随着线虫的死亡,树体水势恢复正常。接种3种线虫虫株后,黑松根系活力随着线虫的侵入都有一个升高的过程,接种强、弱致病力松材线虫虫株后,黑松出现萎蔫时,根系活力虽然有所下降,但仍然保持较好的根系活力,直到松树干枯后根系活力才丧失,这与干旱胁迫下,植物首先丧失根系活力然后表现萎蔫不同;接种无致病力拟松材线虫后,随着拟松材线虫在黑松体内的死亡,黑松的根系活力在升高后逐渐恢复正常。     

松材线虫毒力及发育转型与细胞自噬关系研究

采用透射电镜法对松材线虫的细胞自噬现象进行鉴认,并通过实时定量PCR的方法对不同毒力及不同发育期松材线虫的自噬基因BxAtg1和BxAtg8表达量进行测定。结果表明:饥饿诱导下不同毒力松材线虫存在细胞自噬现象,不同毒力松材线虫饥饿诱导12、24、36 h时,自噬基因BxAtg1表达量递减且趋势一致,而自噬基因BxAtg8在饥饿24 h时的强毒松材线虫体内表达量最高,在饥饿36 h时弱毒松材线虫体内表达量显著升高; 与繁殖性松材线虫体相比,自噬基因BxAtg1和BxAtg8在扩散型3龄(J_Ⅲ)和扩散型4龄幼虫(J_Ⅳ)中的表达量均增加,推测自噬活性的调节机制可能与松材线虫的毒力相关,与松材线虫发育转型阶段的形态特征联系,暗示自噬可帮助松材线虫发育转型,从而提高松材线虫的适应性。     

苯甲酸和苯乙酸对松材线虫及细菌活性的影响

在离体条件下，测定了苯甲酸(BA)和苯乙酸(PA)对马尾松(Pinus massoniana)水培枝叶、松材线虫(Bursaphelenchus xylophilus)及对分离自松材线虫虫体和健康马尾松的细菌菌株GD1和GD2的作用。结果显示，BA和PA对马尾松离体松叶、松枝均具有毒性，其中BA的毒性较强；一定浓度的BA能增强松材线虫的活力，低浓度BA和较高浓度PA均能促进松材线虫的繁殖，低浓度PA能促进菌株GD1的繁殖；高浓度BA和高浓度PA均能抑制松材线虫的活力，其中BA的抑制活性较强；高浓度BA能抑制松材线虫的繁殖，高浓度BA和较高浓度PA均能抑制菌株GD1的繁殖，而BA和PA对菌株GD2繁殖的抑制活性较对菌株GD1的强。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the