锦葵科植物花粉壁的透射电镜观察

本文报道了运用超薄切片法对锦葵科(Malvaceae)七种植物花粉外壁进行透射电镜观察的结果。花粉外壁一般具有两个不同电子密度的层次,电子密度低的是外壁内层,电子密度高、具有结构的部分是外壁外层;内壁内层为无分化结构的板状层。外壁较厚,由外壁内层、柱状层和覆盖层组成。但七种花粉壁的微结构不同。本工作结果表明,运用超薄切片法可以在透射电镜下观察花粉壁的层次、结构、纹饰和萌发孔,也可以看出,不同属种花粉壁的构造是不同的。     

花粉的透射电镜观察

本文报告了运用超薄切片法对有尾水筛、无尾水筛、三棱栎、茅粟、青冈和水青冈六种植物花粉外壁进行透射电镜观察的结果。花粉外壁一般具有两个不同电子密度的层次,电子密度低的是外壁内层,电子密度高,具有结构的部分是外壁外层。内层为板状结构,在萌发孔区明显加厚。外层较厚,由基层、柱状层和覆盖层构成。各种植物花粉外壁的结构不一,有的无覆盖层,有的覆盖层有穿孔。花粉外壁还具有各种纹饰。用电镜还可观察花粉萌发孔的数目、结构和形状。本实验结果表明,运用超薄切片方法可以观察花粉外壁的层次、结构、纹饰和萌发孔。也可看出,不同属种花粉外壁的构造是不相同的。     

润楠花粉内壁超微结构研究

利用TEM对润楠(MachilusPingii Cheng ex Yang)花粉内壁进行了观察,结果表明:四分体解体后的早期小孢子,胼胝质壁内面有高电子致密度物质组成的球状颗粒沉积(图1)。颗粒粒径约27—35nm,高倍率下可见球状颗粒是由一些更为细小的颗粒集聚而成。有微管同球状颗粒联接。小孢子核贴壁分裂时,花粉内壁迅速增厚(图2),增厚的内壁中有呈辐射排列的微通道形成。通道直径约93nm,具较明显的分层通道壁结构,中央有粒径约40nm的椭园球形电子深染团块,通道壁中层与内侧的胼胝质壁相连,椭园球形电子致密团块呈串珠样排列在通道中央(图3)。这一时期花粉内壁中纤维素微纤丝排     

银杏小孢子囊壁发育的超微结构观察

本文利用透射电镜、半薄切片等技术,对银杏小孢子囊壁的发育进行了观察和研究。银杏小孢子囊壁分为表皮、内壁、中层和绒毡层。(1)对小孢子囊壁的表皮、内壁和中层细胞的观察表明,小孢子母细胞时期,这些细胞均处于活跃的代谢和合成阶段,含有大量的细胞器如线粒体、高尔基体、内质网和核糖体等;减数分裂时期细胞的细胞质浓度逐渐降低,细胞内分布有大液泡,其中表皮细胞的液泡膜上形成大量贮藏蛋白,内壁细胞的细胞壁逐渐皱缩,中层细胞纵向拉伸;有丝分裂时期,细胞的细胞质逐渐降解,内壁细胞切向壁和径向壁均出现大量乳突状纤维加厚,中层细胞解体,最后仅剩残余。(2)绒毡层细胞属于分泌型,在小孢子母细胞时期细胞内的细胞器丰富,其中质体在减数分裂过程中达到高峰;游离小孢子时期,粗糙内质网达到最大,绒毡层开始形成乌氏体,最终结合到花粉外壁,参与花粉外壁的形成;有丝分裂后期,绒毡层通过自溶的形式解体。以上结果显示,银杏的小孢子囊壁在为花粉发育提供营养和保护作用方面起着重要作用。     

小麦花药发育过程超微结构和酶细胞化学研究

通常认为是保护组织的药壁表皮和与花粉囊开裂有关的药室内壁细胞 ,在单核花粉粒到花粉粒成熟前夕一直保持着活跃的生命活动状态。细胞内具丰富活力旺盛的细胞器 ,尤其是粗面内质网和囊泡发达的高尔基体以及胞间连丝 ,细胞核、核仁中的ATP酶活性和线粒体内嵴的细胞色素氧化酶活性达到最强。在二细胞后期 ,药壁表皮细胞内出现球型颗粒积累 ,且随着花粉粒的发育逐渐增多 ,以至当花粉粒被淀粉粒充满时 ,该颗粒剧增 ,相当一部分药壁表皮细胞被球型颗粒充满 ,这时药隔薄壁细胞内也有大量的相同颗粒积累。分析认为药壁表皮细胞内的球型颗粒是来自药隔维管细胞营养物质的积累 ,药壁表皮和药室内壁细胞旺盛的代谢活性可能与绒毡层解体和花粉粒对营养物质的需求相关。从四分体到单核花粉粒时期 ,小孢子的发育主要以细胞质的繁殖和体积的增大为主 ,细胞器数量增加不明显 ,线粒体不发达的内嵴上没有细胞色素氧化酶活性 ,细胞核和核仁中有ATP酶活性。第一次有丝分裂完成后 ,花粉粒内壁开始发生 ,内壁的形成需要能量与质膜参与 ,成熟的内壁中具径向的、膜性结构的管状通道 ,在管状通道和外壁的微通道中有显著的ATP酶活性 ,成熟花粉粒萌发孔区的ATP酶活性更显著。二细胞时期 ,花粉粒细胞质活性发生较大的变化 ,各种细     

水稻花粉白苗原质体的超微形态观察

通过透射电镜观察了水稻花药培育产生的白苗、再分化白苗及绿苗,发现花粉绿苗的叶绿体和水稻正常植株的叶绿体在超微形态上是相同的。但是在花粉白苗质体观察中未发现能发育成正常叶绿体的质体中心及发育完好的基粒片层和基质片层。在观察中还发现花粉白苗原质体形成有增殖分裂和直接形成两种方式,但不论哪种方式其初始原质体都具有内、外二层被膜(而每层又都是双层的。)内膜内有大量的核糖核蛋白体。当原质体继续发育时内     

苏云金芽孢杆菌工程菌芽孢形态发生的特征

苏云金芽孢杆菌杀虫蛋白的表达及晶体的形成与芽孢的发育有关。本文利用电子显微镜观察了苏云金芽孢杆菌工程菌不同发育时期芽孢的形态结构特点。结果表明，整个芽孢的发育过程依次经历了前芽孢、双层膜芽孢、初生芽孢壁形成、芽孢衣与孢外壁形成以及皮层形成等过程。这与一般芽孢的发育过程不同，即芽孢衣与孢外壁的形成时期早于皮层；另外发现孢外壁包被有膜结构，这表明杀虫晶体蛋白的超量表达可能会影响到芽孢的发育。     

小麦花药发育过程超微结构和酶结构化学研究

通常认为是保护组织的药壁表皮和与花粉囊开裂有关的药室内壁细胞,在单核花粉粒到花粉粒成熟前夕一直保持着活跃的生命活动状态。细胞内具丰富活力旺盛的细胞器,尤其是粗面内质网和囊泡发达的高尔基体以及胞间连丝,细胞核,核仁中的ATP酶活性和线粒体内嵴的细胞色素酶活性达到最强,在二细胞后期,药壁表皮细胞内出现球型颗粒积累,且随着花粉粒的发育逐渐增多,以至当花粉粒被淀粉粒充满时,该颗粒剧增,相当一部分药壁表皮细胞被球型颗粒充满,这时药隔薄壁细胞内也有大量的相同颗粒积累,分析认为药壁表皮细胞内的球型颗粒是来自药隔维管细胞营养物质的积累,药壁表皮和药室内壁细胞旺盛的代谢活性可能与绒毡层解体和花粉粒对营养物质的需求相关。从四分体到单核花粉粒时期,小孢子的发育主要以细胞质的繁殖和体积的增大为主,细胞器数量增加不明显,线粒不发达的内嵴上没有细胞色素氧化酶活性,细胞核和核仁中有ATP酶活性。第一次有丝分裂完成后,花粉粒内壁开始发生,内壁的形成需要能量与质膜参与,成熟的内壁中具径向的,膜性结构的管状通道,在管状通道和外壁的微通道中有显著的ATP酶活性,成熟花粉粒萌发孔区的ATP酶活性更显著。二细胞时期,花粉粒细胞质活性发生较大的变化。各种细胞器成倍增长,功能明显增强,能量出现自给,代谢达到高潮,线粒体内嵴变得发达,内嵴上出现细胞色素氧化酶活性且逐渐增强,成熟的花粉粒被淀粉粒和内嵴发达具显著细胞色素氧化酶活性的线粒体充满。     

银杏中种皮形态建成及结构特征

由于银杏中种皮的发育及结构与早期种仁形成、后期种核贮藏特性密切相关,本文利用半薄切片和扫描电镜观察了银杏中种皮的分化、发育过程及结构特征。结果表明,银杏授粉后不久珠被分化并形成细胞大小、形态明显差异的3个区,其中中区的5～6层细胞体积小,细胞核大,细胞排列紧密,这几层细胞即将发育形成中种皮;中种皮发育早期,细胞数目增殖速度较快,细胞质染色深,细胞核大并位于细胞的中央;授粉后70d细胞数目不再增加,此时细胞发生径向扩张,随着次生壁的形成,中种皮细胞壁开始加厚;授粉后100d中种皮细胞壁迅速增厚,细胞径向扩张加剧,细胞中央形成完整大液泡,细胞核被挤向靠近细胞壁的部位;之后细胞中液泡破裂,细胞质降解,细胞核解体消失,形成次生壁强烈增厚的多层结构;中种皮发育成熟后由大量管胞组成,根据管胞分布位置的不同可分为螺纹管胞和孔纹管胞2种,管胞侧壁均分布有大量纹孔。     

STM研究Si(111)7×7表面畴界结构

根据对Ｓｉ（１１１）表面各种不同畴界的研究，我们发现并提出了在畴界形成过程中决定这些畴界结构的三个重要因素：二聚体（ｄｉｍｅｒ）和顶戴原子（ａｄａｔｏｍ，亦称吸附原子）之间的相互作用；７×７单胞中层错半单元（ｆａｕｌｔｅｄｈａｌｆ）和非层错半单元（ｕｎｆａｕｌｔｅｄｈａｌｆ）的差异；亚稳态的（２ｎ＋１）×（２ｎ＋１）结构的影响。     

小麦花粉萌发孔与雄性不育关系初探

本文运用扫描电镜和ATP酶细胞化学标记技术，对同核异质和异质同核T型、V型、K型雄性不育系花粉粒萌发孔内、外结构特征以及ATP酶活性分布变化进行了研究。结果不仅观察到花粉粒萌发孔孔盖的突出程度与花粉粒败育的早晚成正相关，而且还观察到萌发孔孔盖与孔环的接触程度与不育系的恢复度有关。进一步分析研究认为萌发孔孔盖突出的不同程度是由萌发孔区Zwischenkorper层与内壁的缺乏和结构异常造成的，微丝的解聚在Zwischenkorper层和内壁两者结构破坏过程中起着重要的作用。     

Characterization of the Ultrathin HfO2 and Hf-Silicate Films Grown by Atomic Layer Deposition

The physical properties of HfO₂ and Hf-silicate layers grown by the atomic layer chemical vapor deposition are characterized as a function of the Hf concentration and the annealing temperature. The peaks of Fourier transform infrared spectra at 960, 900, and 820 cm_-1 originate from Hf-O-Si chemical bonds, revealing that a Hf-silicate interfacial layer began to form at the HfO₂/SiO ₂ interface after post deposition annealing process at 600 degC for 1 min. Moreover, the intensity of the peak at 750 cm^-1 can indicate the degree of crystallization of HfO₂. The formed Hf-silicate layer between HfO² and SiO² is also confirmed by X-ray photoelectron spectroscopy     

铝在不同基因型稻米中的富集

通过环境扫描电镜结合X射线能谱分析技术,对21种不同基因型水稻颖壳内、外表面及糙米表面、糊粉层、近糊粉层和米中部Al含量的测定结果表明,21种不同基因型稻米不同部位Al含量的变化范围由大到小的顺序为:颖壳内表面＞糊粉层＞颖壳外表面＞糙米表面＞近糊粉层＞米中部;不同基因型稻米之间对Al的富集量存在遗传差异,这种差异体现在稻米的同一部位和不同部位之间Al含量的差异上;不同基因型水稻米中部Al含量与糙米表面和近糊粉层Al含量之间、水稻糊粉层Al含量与米中部和近糊粉层Al含量之间以及颖壳内表面Al含量与糊粉层Al含量之间均存在极显著的非线性关系.一方面反映出不同基因型稻米中部Al的富集量均通过颖壳和糊粉层调控,即存在相同的调控机制;另一方面揭示了不同基因型稻米不同部位之间对Al富集的相互调控能力存在差异,并且基因型间的这种差异存在非线性的变化规律.     

银杏花粉萌发生长与分枝式花粉管形成的观察

本研究采用半薄切片法和扫描电镜等技术对银杏（Ginkgo bilobaL.）花粉管的体内萌发与生长以及花粉的离体培养进行了观察,结果表明：（1）银杏花粉粒通过传粉滴收缩后到达胚珠珠孔处,并经珠孔道进入贮粉室内停留,约7 d后花粉粒开始萌发;（2）贮粉室内的花粉最初萌发出的花粉管与花粉粒的四细胞轴几乎垂直,表现出明显的侧向萌发特征。初始花粉管在贮粉室内的生长方向无规律,有的通过一定的贮粉室空间向较远的珠心组织细胞间隙生长,有的直接进到较近的珠心组织细胞间隙,花粉管的生长不损伤珠心组织细胞;（3）花粉离体培养过程中会迅速发生水合作用,花粉粒由船形变为圆球形。48 h后花粉外壁脱落,管细胞膨大,花粉管自管细胞膨大处萌发。随着花粉管的生长,管细胞核移动进入花粉管内,而生殖细胞仍留在花粉粒内。伸长的花粉管可分为淀粉粒区和透明区,花粉管末端易形成多种类型的分枝。花粉管内原生质呈喷泉状流动。     

Silicon nano-asperities: Morphological evolution and electrical properties of double-polysilicon interlayers

Polysilicon/silicon-dioxide/polysilicon structures (double polysilicon) are grown by deposition of amorphous silicon followed by thermal oxidation and a final polysilicon deposition process. Correlation between the appearance of silicon nano-structures and surface morphology formed during the amorphous silicon deposition stage and the electrical characteristics of the double poly capacitor have been investigated. It is shown that the process parameters have a pronounced effect on the morphological properties of the film surface. Nanometric size asperities form during the amorphous silicon deposition stage. The density and height distribution of these asperities were found to depend on deposition temperature. Thermal oxidation of the amorphous layer resulted in the growth of a top oxide layer and crystallization of the bottom silicon film. This process results in an overall increase of the surface roughness and a pronounced decrease in the height of the nano-asperities. By HF-etching the oxidized film, the surface of the polycrystalline silicon is exposed. Following this etching process, the surface roughness increases, whereas the density and height of the nano-asperities decrease. A correlation between the height of asperities on the bottom amorphous silicon film (as well as roughness of this film) and the breakdown voltage of the double poly was found.     

Phase field simulations of morphological evolution and growth kinetics of solder reaction products

Two-dimensional simulations of the morphological and growth evolutions of the intermetallic compound (IMC) formed between a Sn-based solder and a Cu pad are performed using a multiphase field model, in order to examine the difference between the IMC growth behavior for the soldering reaction and that for the solid-state aging after soldering. The simulations show that the scallop-type IMC morphology formed in the soldering reaction is governed not only by the surface energy difference between the solder/IMC interface and the IMC grain boundary (GB), but also by the difference in diffusivities in the liquid solder and the IMC GB. It is also shown that the orders of magnitude difference in the IMC growth rate between the soldering reaction and the subsequent aging process is mainly attributed to the increased IMC GB distance resulting from the morphological change of the IMC from a scallop type to a layer type. The change in the solder diffusivity itself, however, has only a minor influence on the IMC growth kinetics of the layer-type IMC in the subsequent aging process.     

Surface Nanostructures Forming during the Early Stages of the Metal-Assisted Chemical Etching of Silicon. Optical Properties of Silver Nanoparticles

In this two-part work, nanostructures formed in a three-step process of metal-assisted chemical etching of silicon are investigated. In the first part (present publication), the process of the chemical deposition of a layer of self-assembled silver nanoparticles on the surface of a silicon wafer (the first stage of metalassisted chemical etching) is studied. This layer, on the one hand, serves as a catalyst for the subsequent etching of silicon, and, on the other hand, represents a kind of mask for the formation of a certain topology of the emerging Si nanowires. The morphology of the obtained 40- to 60-nm-thick silver nanoparticle layers is investigated by scanning electron microscopy. The spectral dependences of the ellipsometric angles Ψ and Δ are measured using spectroscopic ellipsometry (λ = 250–900nm), and the complex dielectric function of the silver nanolayers is determined from these spectra. The dielectric function features a characteristic plasmon resonance peak in the ultraviolet spectral range. The study of the optical properties of Si nanofilament layers which form during the early stages of metal-assisted chemical etching will be reported as the second part of this work in a separate publication.     

'秦冠'苹果花粉培养及微丝骨架的变化

以'秦冠'苹果花粉为试材,采用花粉离体培养法,研究了不同培养基组分以及温度对苹果花粉萌发的影响.结果表明:(1)蔗糖和硼酸在一定质量浓度范围内,对苹果花粉萌发及花粉管生长起促进作用,但超过一定质量浓度时则起抑制作用.秦冠苹果花粉最适的培养基为20%蔗糖和0.01%硼酸,花粉的萌发率可以达到60%.在此基础上,以Alexa Fluor 488phalloidin作为肌动蛋白微丝的探针,运用激光共聚焦显微镜技术,观察了苹果花粉萌发过程中微丝骨架的分布变化动态;(2)在未水合的苹果花粉粒中,均匀分布着短小弯曲、颗粒环形微丝.在水合而未萌发的的花粉中,微丝呈网状分布在胞质中,萌发沟部分肌动蛋白束网络较致密,中央胞质部分较疏松.花粉萌发后,微丝转变为平行排列,向花粉管伸长的方向延伸聚集,与花粉管纵向平行排列;(3)生长异常的花粉管内其微丝状态也异常.     

IEEE standard 802.16: a technical overview of theWirelessMANTM air interface for broadband wirelessaccess

The broadband wireless access industry, which provides high-rate network connections to stationary sites, has matured to the point at which it now has a standard for second-generation wireless metropolitan area networks. The IEEE standard 802.16, with its WirelessMAN^TM air interface, sets the stage for widespread and effective deployments worldwide. This article overviews the technical medium access control and physical layer features of this new standard     

Formation of Spherical and Non‐Spherical Eutectic Gallium‐Indium Liquid‐Metal Microdroplets in Microfluidic Channels at Room Temperature

Here, the formation of eutectic Gallium‐Indium (EGaIn) liquid‐metal microdroplets, both spherical and non‐spherical, in microfluidic devices at room temperature is reported. Monodisperse microdroplets were created in an aqueous polyethylene glycol (PEG) solution, in oxygenated and in deoxygenated silicone oil. The volume of the droplets depends on the channel dimensions and flow rates applied, varying between 0.5 and 4 nL. Non‐spherical droplets were formed in oxygenated silicone oil due to the instantaneous formation of an oxide layer. These metal “micro‐rice” droplets retained their shape and did not spontaneously reflow to form shapes of the lowest interfacial energy on egress from the channel, unlike in aqueous PEG solution and in deoxygenated silicone oil. Liquid‐metal droplets with such tunable morphology can potentially be used in MEMS devices for optical and electrical switches, valves and micropumps.