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1.
High-resolution transmission electron microscopy and scanning tunneling microscopy have been combined to examine the structure of the thin "native" oxide that forms on silicon surfaces at room temperature. Differences in the cleaning procedures for silicon wafers may affect the morphology of this oxide and critically influence further processing on the silicon substrates. An etch that ended with a dip in hydrofluoric acid provided a thinner oxide and a lower interface step density than did a sulfuric peroxide treatment. The availability of complementary information from high-resolution transmission electron microscopy and scanning tunneling microscopy is discussed. 相似文献
2.
A link between scanning tunneling microscopy (STM) and conventional transmission electron microscopy has been established for biological material by applying STM on freeze-dried recA-DNA complexes coated with a conducting film. The topography of the complexes observed by means of STM revealed a right-handed single helix composed of about six recA monomers per helical turn. 相似文献
3.
鲽形目鱼类仔鱼经过变态后形成眼睛和偶鳍等器官左右不对称的稚鱼。Tbx家族成员参与脊椎动物心脏、肢体和眼等器官的发育,而Tbx基因与鲽形目鱼类变态的关系目前尚无报道。我们运用扫描电镜和软硬骨染色等方法对出膜后2d（变态早期）和26d（变态前期）的牙鲆仔鱼的形态进行观察,牙鲆出膜后2d胸鳍原基出现,出膜后26d胸鳍发育成熟,而在出膜后26d胸鳍和腹鳍仍呈现左右对称。我们克隆了牙鲆Tbx5基因的CDS序列,该序列编码的多肽具有部分T-box保守结构域,与斑马鱼Tbx5同源性高达93%。系统进化分析显示：这段CDS序列与硬骨鱼的Tbx5基因聚为一支,但与四足动物Tbx5相分离。整体原位杂交显示出膜后26d的牙鲆仔鱼中,Tbx5基因不仅在胸鳍、眼背侧、脊柱和尿囊表达,且在胸鳍和眼背侧的表达呈现左右不对称,左侧面（有眼侧）的表达量均高于右侧面（无眼侧）的表达量。综上结果暗示,牙鲆Tbx5基因可能参与了变态过程中眼睛与胸鳍左右不对称的形成。
研究亮点： 鲽形目鱼类都经历变态发育过程,产生显著的左右不对称形态,但调控该过程的分子机制尚不清楚。本文对牙鲆变态初期仔鱼进行了形态学观察,并对牙鲆Tbx5进行克隆及其表达分析,并探讨Tbx5与牙鲆仔鱼眼睛与胸鳍不对称变态过程的关系,为进一步研究牙鲆变态机制奠定基础。 相似文献
4.
A new type of tapetum lucidum has been found in eyes of bony fishes (teleosts). It is retinal, lying in the processes of the pigment epithelial cells; it has a white appearance and reflects light diffusely. The cell processes are loaded with highly refractile lipid particles; as examined by electron microscopy these are about 400 nanometers in diameter, spherical, and homogeneous. This tapetum lucidum has been found in seven families of teleost fishes occurring in inshore waters and rivers of South Texas, all of which have high turbidity; the correlation indicates a role in dim-light vision. 相似文献
5.
Erythrocytes: pits and vacuoles as seen with transmission and scanning electron microscopy 总被引：3，自引：0，他引：3
Vacuoles containing inclusions were observed by transmission electron microscopy in erythrocytes of a splenectomized patient with hemoglobin Ann Arbor. The membranes of these vacuoles became fused with the surface membrane of the red cell, thus opening the vacuoles and exposing their contents to the outside. These vacuoles when they have become thus attached to the cell membrane of the erythrocyte are responsible for the pits observed with scanning electron microscopy. 相似文献
6.
应用显微硬度、光学显微镜、X射线衍射、SEM及 AES等,分析与研究了大型铁路轴承(197 726)表面变质层的成分、组织与残余应力,发现变质层中硬度的变化与磨削热产生的相变及表层碳量下降有关,表面存在很大残余压应力,但分布不均匀。 相似文献
7.
A chemoautotrophic, thermophilic, and acidophilic microorganism capable of oxidizing reduced sulfur and iron compounds and leaching concentrates of molybdenite and chalcopyrite at 60 degrees C has been characterized by transmission and scanning electron microscopy. This constitutes the first direct observations of microorganisms on ore fines. 相似文献
8.
The dissolution of polyhedra of Mythimna separata nuclear polyhedrosis.virus by digestive fluid(pH 11.03) collected from the 5th instar M.separata larvae was studied.in vitro.Observations were made at timed intervals using phase contrast microscopy and scanning electron microscopy.Under phase contrast microscopy,the polyhedra lost their refrigence by 5minute exposure to the digestive fluid.After exposure to the fluid for 30 minutes,all of the PIBs were dissolved.Chages of the PIBs were also observed under scanning electron microscopy,after 5 minute exposure to the fluid,damaged PIBs and PIB-derived debris were seen,After 30 minute exposure,only remains of PIBs were found .The effect of M.separata digestive fluid on the infectivity of Ms NPV was examined by neonates bioassay.The results indicated that virions from Ms NPV-PIBs were rapidly inactivated after 15 minute exposure to digestive fluid and all of virons were non-infectious. 相似文献
9.
Nellist PD Chisholm MF Dellby N Krivanek OL Murfitt MF Szilagyi ZS Lupini AR Borisevich A Sides WH Pennycook SJ 《Science (New York, N.Y.)》2004,305(5691):1741
Despite the use of electrons with wavelengths of just a few picometers, spatial resolution in a transmission electron microscope (TEM) has been limited by spherical aberration to typically around 0.15 nanometer. Individual atomic columns in a crystalline lattice can therefore only be imaged for a few low-order orientations, limiting the range of defects that can be imaged at atomic resolution. The recent development of spherical aberration correctors for transmission electron microscopy allows this limit to be overcome. We present direct images from an aberration-corrected scanning TEM that resolve a lattice in which the atomic columns are separated by less than 0.1 nanometer. 相似文献
10.
H N Guttman 《Science (New York, N.Y.)》1971,171(968):290-292
Simple washing of live Euglena gracilis cleans the pellicle of external coating material. When these cleaned cells are viewed with a scanning electron microscope, organelle outlines can be seen through the thinned pellicle. To view organelles directly, fixed Euglena cells are gently broken first or first frozen and then broken as part of their preparation for scanning electron microscopy. Subsequent viewing at magnifications of x 5,000 to x 21,000 reveals organelles, storage granules, endoplasmic reticulum, and nuclear pores, while retaining great depth of focus. 相似文献
11.
The relative effect of light in inducing downward movements of the tips of isolated arms of Asterias amurensis is maximal at 485 millimicrons when the compound ocellus is intact; at 504 millimicrons when the ocellus has been removed. This finding suggests the coexistence of two photoreceptive systems, ocellar and nonocellar. 相似文献
12.
[目的]采用扫描电镜观察双角螺旋线虫（Helicotylenchus digonicus）。[方法]对采自浙江长兴的双角螺旋线虫进行了扫描电镜观察,对光镜下的形态结构进行了确认。[结果]采用戊二醛-锇酸双固定及临界点干燥制备的线虫样本,虫体不皱缩,不变形,形态结构清晰,能够很好地进行扫描电镜观察。[结论]为研究和防治双角螺旋线虫提供了参考。 相似文献
13.
为了探究与老鹳草相关类型花粉花芽的样品电镜制备,采用直接观察法和戊二醛固定冷冻干燥法对青岛老鹳草花粉扫描电镜制样条件进行了研究。结果表明：直接观察法制备的青岛老鹳草花粉颗粒在扫描电镜下形态饱满,结构清晰,花粉表面的纹饰和突起微观结构清晰完整;改进的FAA单固定冷冻干燥法处理的青岛老鹳草花芽形态学结构完整,层次丰富,立体感强,细胞失水皱缩得到明显改善。通过对不同制样方法进行比较,最终得到可靠简单易行的样品制备方法,对牦牛儿苗科植物的研究及相关类型花粉花芽的样品制备有重要的指导意义。 相似文献
14.
The magnetic properties of surfaces are now being explored with electron spectroscopies that use electron spin polarization techniques. The increased activity in surface magnetic measurements with polarized electron beams is spurred by new scientific and technological challenges and is made feasible by recent advances in the technology of sources and detectors of polarized electrons. The ability to grow thin films and to engineer artificial structures permits new phenomena to be investigated at magnetic surfaces and interfaces. For such investigations, spin-polarized electron techniques-such as polarized electron scattering, polarized photoemission, polarized Auger spectroscopy, and scanning electron microscopy with polarization analysis-have been and will probably continue to be used to great advantage. 相似文献
15.
刘玟妍 《中国农业文摘-农业工程》2019,31(4):61-64
目的:应用扫描电子显微镜技术对沙苑子及其伪品紫云英子超微结构进行研究,建立沙苑子的超微指纹鉴别方法。方法:分别在35倍、800倍、3 000倍电镜下观察沙苑子正品(扁茎黄芪种子)及其伪品紫云英子的超微指纹特征,并进行对比分析研究。结果:沙苑子和紫云英子在颜色、形状上略有差异,在扫描电镜下观察其超微结构有显著差异。结论:本研究建立的超微指纹鉴别方法可简便、快速、准确的区分沙苑子和紫云英子,为沙苑子药材鉴别提供科学依据。 相似文献
16.
将果蝇置于含印楝素2 mg/kg的昆虫培养基中产卵,待卵孵化发育至不同虫态,运用光学显微镜及扫描电镜研究果蝇新羽化成虫复眼外观,发现复眼明显萎缩并呈现不规则状,表面粗糙,出现异常凹陷,刚毛缺失或增生,排列不规则或弯曲;运用透射电镜研究复眼超微结构,结果表明,3龄末期幼虫复眼组织细胞中染色质高度聚集成小体、小体分散,吞噬泡数量明显增多,核膜皱缩、界限模糊,蛹和新羽化成虫复眼中感光细胞丢失.这些结果确证了印楝素诱导果蝇复眼发育异常,为寻找新型昆虫生长发育调节剂提供了可能的新靶标. 相似文献
17.
A combination of chemical vapor deposition and scanning tunneling microscopy techniques have been used to produce nanometer-scale, iron-containing deposits with high aspect ratios from an iron pentacarbonyl precursor both on a substrate and on the tunneling tip itself. The structure and composition of the resulting nanodeposits were determined by transmission electron microscopy and high spatial resolution Auger electron spectroscopy. Either polycrystalline, relatively pure, body-centered-cubic iron or disordered carbon-rich material can be deposited, depending on the bias conditions of the tip sample junction and the precursor pressure. Two mechanisms of decomposition are inferred from the growth phenomenology. 相似文献
18.
Davis RE Worley JF Whitcomb RF Ishijima T Steere RL 《Science (New York, N.Y.)》1972,176(4034):521-523
Mycoplasma-like bodies with helical filaments were seen by phase contrast microscopy in juice expressed from tissues of plants infected with corn stunt agent. Each filament is bounded by a "unit membrane" and no cell wall, sheath, envelope, or second membrane has yet been discerned by electron microscopy. The association of these filaments with development of disease, their occurrence in phloem cells as seen by both freeze-etching and thin-section electron microscopy, the diagnosis of infection based on their presence in plants without symptoms, and their absence in noninfected corn are consistent with the hypothesis that these unusual filaments are formed by the mycoplasma-like organism presumed to be the corn stunt agent. 相似文献
19.
Deheer WA Bacsa WS Châtelain A Gerfin T Humphrey-Baker R Forro L Ugarte D 《Science (New York, N.Y.)》1995,268(5212):845-847
Carbon nanotube material can now be produced in macroscopic quantities. However, the raw material has a disordered structure, which restricts investigations of both the properties and applications of the nanotubes. A method has been developed to produce thin films of aligned carbon nanotubes. The tubes can be aligned either parallel or perpendicular to the surface, as verified by scanning electron microscopy. The parallel aligned surfaces are birefringent, reflecting differences in the dielectric function along and normal to the tubes. The electrical resistivities are anisotropic as well, being smaller along the tubes than perpendicular to them, because of corresponding differences in the electronic transport properties. 相似文献
20.
制备叶表皮观察样品技术的改进 总被引：2，自引：0，他引：2
贺晓 《内蒙古林学院学报》1997,19(2):23-26
本文介绍了观察叶表皮内表面的方法，用此方法制备的样品可供光镜和扫描电镜观察叶表皮细胞内表皮的形态结构，特别是保卫结构的形态结构。 相似文献