共查询到20条相似文献，搜索用时 656 毫秒
1.
【目的】探索斑马鱼性腺经不同染色剂染色后在不同激发光激发下的荧光特性。【方法】以斑马鱼性腺为材料，用Bouin's液固定，石蜡切片未经染色或单染伊红、单染苏木精、HE染色后，分别在白光（明场）、绿色激发光、蓝色激发光和紫外激发光下观察斑马鱼性腺的荧光特性。【结果】未染色的斑马鱼性腺组织切片，经不同激发光激发后，可观察到自发产生较弱的荧光；而以单染伊红、单染苏木精或HE染色后，经不同激发光激发，斑马鱼性腺中的生殖细胞和体细胞分别呈现不同的荧光特性，且不同染色切片经相应的激发光激发后所发出的荧光及细胞结构的清晰度均存在明显差异。【结论】将组织学技术中最常用的苏木精和伊红染色方法与荧光技术、荧光观察结合起来，可更简易而快速区分不同细胞类型、不同细胞周期等。 相似文献
2.
【目的】探索斑马鱼性腺经不同染色剂染色后在不同激发光激发下的荧光特性。【方法】以斑马鱼性腺为材料,用Bouin＇s液固定,石蜡切片未经染色或单染伊红、单染苏木精、HE染色后,分别在白光（明场）、绿色激发光、蓝色激发光和紫外激发光下观察斑马鱼性腺的荧光特性。【结果】未染色的斑马鱼性腺组织切片,经不同激发光激发后,可观察到自发产生较弱的荧光;而以单染伊红、单染苏木精或HE染色后,经不同激发光激发,斑马鱼性腺中的生殖细胞和体细胞分别呈现不同的荧光特性,且不同染色切片经相应的激发光激发后所发出的荧光及细胞结构的清晰度均存在明显差异。【结论】将组织学技术中最常用的苏木精和伊红染色方法与荧光技术、荧光观察结合起来,可更简易而快速区分不同细胞类型、不同细胞周期等。 相似文献
3.
Two-photon laser scanning fluorescence microscopy 总被引：126，自引：0，他引：126
Molecular excitation by the simultaneous absorption of two photons provides intrinsic three-dimensional resolution in laser scanning fluorescence microscopy. The excitation of fluorophores having single-photon absorption in the ultraviolet with a stream of strongly focused subpicosecond pulses of red laser light has made possible fluorescence images of living cells and other microscopic objects. The fluorescence emission increased quadratically with the excitation intensity so that fluorescence and photo-bleaching were confined to the vicinity of the focal plane as expected for cooperative two-photon excitation. This technique also provides unprecedented capabilities for three-dimensional, spatially resolved photochemistry, particularly photolytic release of caged effector molecules. 相似文献
4.
Baker S Robinson JS Haworth CA Teng H Smith RA Chirila CC Lein M Tisch JW Marangos JP 《Science (New York, N.Y.)》2006,312(5772):424-427
We demonstrate a technique that uses high-order harmonic generation in molecules to probe nuclear dynamics and structural rearrangement on a subfemtosecond time scale. The chirped nature of the electron wavepacket produced by laser ionization in a strong field gives rise to a similar chirp in the photons emitted upon electron-ion recombination. Use of this chirp in the emitted light allows information about nuclear dynamics to be gained with 100-attosecond temporal resolution, from excitation by an 8-femtosecond pulse, in a single laser shot. Measurements on molecular hydrogen and deuterium agreed well with calculations of ultrafast nuclear dynamics in the H2+ molecule, confirming the validity of the method. We then measured harmonic spectra from CH4 and CD4 to demonstrate a few-femtosecond time scale for the onset of proton rearrangement in methane upon ionization. 相似文献
5.
The reaction K + NaBr --> KBr + Na is probed during the reactive collision by a continuous wave laser tuned to frequencies not resonant with excitation in either reagents or products. Transient [K..Br..Na] absorbs a laser photon giving [K..Br..Na](*), which can decompose to Na(*) + KBr. Emission from excited Na(*) at the sodium D lines provides direct evidence of laser absorption during the reaction. Different excitation spectra were observed, depending on which sodium D line was monitored. This difference is explicable if, in the absence of the laser, the reaction flux partially bifurcates to a second potential energy surface during the reaction. 相似文献
6.
拟采取的罐装绿茶水生产工艺特点是：茶鲜叶绿杀青后,直接烘干作为原料,避光真空沸水浸出,通过研究发现,杀青后直接烘干的处理样在色泽、香气、滋味上均优于炒青绿茶对照样;避光真空浸出有利于茶汤护色;避光人无离子水浸出在减少沉淀产生方面有明显效果,同时还发现,烘干的处理样出现高浓的熟栗香;避光真空条件下自来水同的汤色比无离子浸出的汤色绿色度高。 相似文献
7.
The roles of structural imperfections in InGaN-based blue light-emitting diodes and laser diodes 总被引：2，自引：0，他引：2
S Nakamura 《Science (New York, N.Y.)》1998,281(5379):955-961
REVIEW High-efficiency light-emitting diodes emitting amber, green, blue, and ultraviolet light have been obtained through the use of an InGaN active layer instead of a GaN active layer. The localized energy states caused by In composition fluctuation in the InGaN active layer are related to the high efficiency of the InGaN-based emitting devices. The blue and green InGaN quantum-well structure light-emitting diodes with luminous efficiencies of 5 and 30 lumens per watt, respectively, can be made despite the large number of threading dislocations (1 x 10(8) to 1 x 10(12) cm-2). Epitaxially laterally overgrown GaN on sapphire reduces the number of threading dislocations originating from the interface of the GaN epilayer with the sapphire substrate. InGaN multi-quantum-well structure laser diodes formed on the GaN layer above the SiO2 mask area can have a lifetime of more than 10,000 hours. Dislocations increase the threshold current density of the laser diodes. 相似文献
8.
对杂交稻亲本进行遗传标记,以便在发生杂交稻亲本相互混杂,或发生机械混杂,或发生其它人为因素混杂时能轻易地根据亲本的标记性状进行去杂,以保证杂交种的高纯度,基于该项考虑,我们利用辐射育种材料中出现的淡黄绿叶水稻突变体,来选育带有该特殊标记的粳稻三系不育系和保持系,进而利用它来研制可供生产应用的杂粳组合,我们选用的淡黄绿叶水稻突变体其叶色自苗期至成熟期始终呈淡黄绿色,与正常水稻的绿色极易区分,用它与正常水稻杂交,其F1代苗呈正常绿色,F2代苗中绿色与淡黄绿叶苗的比例接近于3∶1,绿色表现为显性,淡黄绿叶色为隐性,而且很可能是受一对隐性基因控制。 相似文献
9.
果蝇生殖包囊固定染色后的荧光特性（摘要） 总被引：1，自引：0，他引：1
[目的]探索果蝇卵巢及生殖包囊经过常规固定和染色后的荧光特性,为荧光组织学的发展提供第一手资料。[方法]以黑腹果蝇卵巢为试验材料,用Bouin氏液固定,石蜡切片后分别用HE、苏木精、伊红染色,分别在明场（白光）、绿色、蓝色和紫外激发光下观察、拍照。[结果]3种方法染色后,再经不同激发光激发,生殖细胞和体细胞可发出不同颜色的荧光,细胞中脂类、核酸及蛋白质也可分别发出各自特异性的荧光。[结论]常规染色剂可以分别赋予生殖细胞和体细胞各自不同的荧光特性,也可赋予细胞内不同物质成份各自不同的荧光特性。 相似文献
10.
A broadly tunable picosecond laser source and an ultrafast streak camera were used to measure temporally and spectrally resolved emission from intact phycobilisomes and from individual phycobiliproteins as a function of excitation wavelength. Both wild-type and mutant phycobilisomes of the unicellular cyanobacterium Synechocystis 6701 were examined, as well as two biliproteins, R-phycoerythrin (240 kilodaltons, 34 bilins) and allophycocyanin (100 kilodaltons, 6 bilins). Measurements of intact phycobilisomes with known structural differences showed that the addition of an average of 1.6 phycoerythrin disks in the phycobilisome rod increased the overall energy transfer time by 30 +/- 5 picoseconds. In the isolated phycobiliproteins the onset of emission was as prompt as that of a solution of rhodamine B laser dye and was independent of excitation wavelength. This imposes an upper limit of 8 picoseconds (instrument-limited) on the transfer time from "sensitizing" to "fluorescing" chromophores in these biliproteins. These results indicate that disk-to-disk transfer is the slowest energy transfer process in phycobilisomes and, in combination with previous structural analyses, show that with respect to energy transfer the lattice of approximately 625 light-harvesting chromophores in the Synechocystis 6701 wild-type phycobilisome functions as a linear five-point array. 相似文献
11.
Interfering light waves produce an optical interference pattern in any medium that interacts with light. This modulation of some physical parameter of the system acts as a classical holographic grating for optical radiation. When such a grating is produced through interaction of pulsed light waves with an optical transition, a transient grating is formed whose decay is a measure of the relaxation time of the excited state. Transient gratings can be formed in real space or in frequency space depending on the time ordering of the interfering light waves. The two gratings are related by a space-time transformation and contain complementary information on the optical dynamics of a system. The status of a grating can be probed by a delayed third pulse, which diffracts off this grating in a direction determined by the wave vector difference of the interfering light beams. This generalized concept of a transient grating can be used to interpret many picosecond-pulse optical experiments on condensed-phase systems. Examples of some low-temperature experiments will be presented. In principle, many of these experiments could also be performed by using stochastic broad-band excitation. In these nonlinear photon-interference experiments the time resolution is determined by the correlation time of the light source rather than its pulse width. 相似文献
12.
Conventional laser cooling relies on repeated electronic excitations by near-resonant light, which constrains its area of application to a selected number of atomic species prepared at moderate particle densities. Optical cavities with sufficiently large Purcell factors allow for laser cooling schemes, avoiding these limitations. Here, we report on an atom-cavity system, combining a Purcell factor above 40 with a cavity bandwidth below the recoil frequency associated with the kinetic energy transfer in a single photon scattering event. This lets us access a yet-unexplored regime of atom-cavity interactions, in which the atomic motion can be manipulated by targeted dissipation with sub-recoil resolution. We demonstrate cavity-induced heating of a Bose-Einstein condensate and subsequent cooling at particle densities and temperatures incompatible with conventional laser cooling. 相似文献
13.
Kienberger R Hentschel M Uiberacker M Spielmann Ch Kitzler M Scrinzi A Wieland M Westerwalbesloh T Kleineberg U Heinzmann U Drescher M Krausz F 《Science (New York, N.Y.)》2002,297(5584):1144-1148
Photoelectrons excited by extreme ultraviolet or x-ray photons in the presence of a strong laser field generally suffer a spread of their energies due to the absorption and emission of laser photons. We demonstrate that if the emitted electron wave packet is temporally confined to a small fraction of the oscillation period of the interacting light wave, its energy spectrum can be up- or downshifted by many times the laser photon energy without substantial broadening. The light wave can accelerate or decelerate the electron's drift velocity, i.e., steer the electron wave packet like a classical particle. This capability strictly relies on a sub-femtosecond duration of the ionizing x-ray pulse and on its timing to the phase of the light wave with a similar accuracy, offering a simple and potentially single-shot diagnostic tool for attosecond pump-probe spectroscopy. 相似文献
14.
Sanvitto D Pulizzi F Shields AJ Christianen PC Holmes SN Simmons MY Ritchie DA Maan JC Pepper M 《Science (New York, N.Y.)》2001,294(5543):837-839
We report transport of electron-hole complexes in semiconductor quantum wells under applied electric fields. Negatively charged excitons (X-), created by laser excitation of a high electron mobility transistor, are observed to drift upon applying a voltage between the source and drain. In contrast, neutral excitons do not drift under similar conditions. The X- mobility is found to be as high as 6.5 x 10(4) cm2 V-1 s-1. The results demonstrate that X- exists as a free particle in the best-quality samples and suggest that light emission from opto-electronic devices can be manipulated through exciton drift under applied electric fields. 相似文献
15.
Michler P Kiraz A Becher C Schoenfeld WV Petroff PM Zhang L Hu E Imamoglu A 《Science (New York, N.Y.)》2000,290(5500):2282-2285
Quantum communication relies on the availability of light pulses with strong quantum correlations among photons. An example of such an optical source is a single-photon pulse with a vanishing probability for detecting two or more photons. Using pulsed laser excitation of a single quantum dot, a single-photon turnstile device that generates a train of single-photon pulses was demonstrated. For a spectrally isolated quantum dot, nearly 100% of the excitation pulses lead to emission of a single photon, yielding an ideal single-photon source. 相似文献
16.
Clarkson JR Baquero E Shubert VA Myshakin EM Jordan KD Zwier TS 《Science (New York, N.Y.)》2005,307(5714):1443-1446
The two-step laser excitation scheme of stimulated emission pumping (SEP) induces shifts of a single water molecule between two remote hydrogen bonding sites on trans-formanilide. This reaction can be initiated by selective excitation of either isomer (CO-bound or NH-bound) with different SEP excitation wavelengths. Energy (E) thresholds for isomerization in both directions have been measured [796 wave numbers NH) CO) 相似文献
17.
Gibson EA Paul A Wagner N Tobey R Gaudiosi D Backus S Christov IP Aquila A Gullikson EM Attwood DT Murnane MM Kapteyn HC 《Science (New York, N.Y.)》2003,302(5642):95-98
We demonstrate enhanced generation of coherent light in the "water window" region of the soft x-ray spectrum at 4.4 nanometers, using quasi-phase-matched frequency conversion of ultrafast laser pulses. By periodically modulating the diameter of a gas-filled hollow waveguide, the phase mismatch normally present between the laser light and the generated soft x-ray light can be partially compensated. This makes it possible to use neon gas as the nonlinear medium to coherently convert light up to the water window, illustrating that techniques of nonlinear optics can be applied effectively in the soft x-ray region of the spectrum. These results advance the prospects for compact coherent soft x-ray sources for applications in biomicroscopy and in chemical spectroscopy. 相似文献
18.
笔者将激光技术应用于森林勘测,研制出具有可见光导向、激光测距和坡面直读水平距三项主要功能的新型测量工具。本仪由发射系统和接收系统两部分组成。发射系统发射出红色激光束,在森林环境中设置出既定方位的可见方向线,作业人员可按照红色光斑的指示砍伐测线。激光束通过半楔形透镜,分为具有一定夹角的两束光,在接收杆上直接读取实际距离值。在坡面上测量时,若接收杆垂直于水平面,读数为斜距。若接收杆垂直于坡面,读数则为水平距。利用遮光罩或定角器可以保证接收杆垂直于坡面,发明了在坡面上测距不经斜距换算而直接获得水平距的新技术。 相似文献
19.
Arnold W 《Science (New York, N.Y.)》1966,154(3752):1046-1049
Frozen green plants (Chlorella) carry out a photoreaction which can be assayed by measuring the light produced when the sample is heated. Heating at a rate of several degrees per second gives a measurable signal which shows that green plants can store energy at very low temperatures. The absorption cross section for the unit which carries out the photoreaction is several hundred times larger than that for one chlorophyll molecule, an indication that these are the "photosynthetic units" of photosynthesis. 相似文献
20.
The laser-induced movement of CO molecules over a platinum surface was followed in real time by means of ultrafast vibrational spectroscopy. Because the CO molecules bound on different surface sites exhibit different C-O stretch vibrational frequencies, the site-to-site hopping, triggered by excitation with a laser pulse, can be determined from subpicosecond changes in the vibrational spectra. The unexpectedly fast motion--characterized by a 500-femtosecond time constant--reveals that a rotational motion of the CO molecules, rather than pure translation, is required for this diffusion process. This conclusion is corroborated by density functional theory calculations. 相似文献