Time-resolved holography with photoelectrons

Ionization is the dominant response of atoms and molecules to intense laser fields and is at the basis of several important techniques, such as the generation of attosecond pulses that allow the measurement of electron motion in real time. We present experiments in which metastable xenon atoms were ionized with intense 7-micrometer laser pulses from a free-electron laser. Holographic structures were observed that record underlying electron dynamics on a sublaser-cycle time scale, enabling photoelectron spectroscopy with a time resolution of almost two orders of magnitude higher than the duration of the ionizing pulse.     

Applied physics. Subsurface imaging with scanning ultrasound holography

Every new microscopic imaging technique reveals hidden features but also new challenges. To capture information about substructure features, especially defects and voids, in the next generation of integrated circuits, higher resolution methods of surface imaging will be required. In his Perspective, Diebold discusses results reported in the same issue by Shekhawat and Dravid in which an acoustic scanning holographic imaging technique has been extended to unprecedented spatial resolution. The method has also been used on biological cells, and the hope is that it can be developed further to obtain detailed information about the depth and elastic properties of buried features.     

Atomic images by electron-wave holography

Direct views of electron clouds in atoms h-ave been observed visually and photographed by means of a two-stage holographic miscroscope based on Gabor's principle of image reconstruction. Holograms are produced with 40-kilo-volt electron radiation and decoded with an optical laser. The obviation of an objective lens makes feasible a numerical aperture of 0.37 and a resolving power exceeding 0.1 angstrom.     

Human perception of illumination with pulsed ultrahigh-frequency electromagnetic energy

A psychophysical study of the perception of "sound" induced by illumination with pulse-modulated, ultrahigh-frequency electromagnetic energy indicated that perception was primarily dependent upon peak power and secondarily dependent upon pulse width. The average power did not significantly affect perception. Perceived characteristics of pitch and timbre appeared to be functions of modulation.     

Magnetic microstructure of magnetotactic bacteria by electron holography

Off-axis electron holography in the transmission electron microscope was used to correlate the physical and magnetic microstructure of magnetite nanocrystals in magnetotactic bacteria. The magnetite crystals were all single magnetic domains, and the magnetization directions of small superparamagnetic crystals were constrained by magnetic interactions with larger crystals in the chains. Shape anisotropy was found to dominate magnetocrystalline anisotropy in elongated crystals. A coercive field between 300 and 450 oersted was determined for one chain.     

Subdiffraction multicolor imaging of the nuclear periphery with 3D structured illumination microscopy

Fluorescence light microscopy allows multicolor visualization of cellular components with high specificity, but its utility has until recently been constrained by the intrinsic limit of spatial resolution. We applied three-dimensional structured illumination microscopy (3D-SIM) to circumvent this limit and to study the mammalian nucleus. By simultaneously imaging chromatin, nuclear lamina, and the nuclear pore complex (NPC), we observed several features that escape detection by conventional microscopy. We could resolve single NPCs that colocalized with channels in the lamin network and peripheral heterochromatin. We could differentially localize distinct NPC components and detect double-layered invaginations of the nuclear envelope in prophase as previously seen only by electron microscopy. Multicolor 3D-SIM opens new and facile possibilities to analyze subcellular structures beyond the diffraction limit of the emitted light.     

Enhanced sensitivity of photodetection via quantum illumination

The use of quantum-mechanically entangled light to illuminate objects can provide substantial enhancements over unentangled light for detecting and imaging those objects in the presence of high levels of noise and loss. Each signal sent out is entangled with an ancilla, which is retained. Detection takes place via an entangling measurement on the returning signal together with the ancilla. This paper shows that for photodetection, quantum illumination with m bits of entanglement can in principle increase the effective signal-to-noise ratio by a factor of 2(m), an exponential improvement over unentangled illumination. The enhancement persists even when noise and loss are so great that no entanglement survives at the detector.     

全息玉米种增产新途径--张春庆博士谈生物全息律与全息玉米种

种子是重要的农业生产资料，选好用好种子是一项非常有效的增产措施。山东农业大学农学院在农作物种子方面做了大量的工作，特别是用高新生物全息理论指导选种技术，提高选种效果，取得了显著的社会效益和经济效益。北京神农科诺种子公司是全国第一家以研究、开发全息玉米种子的高新技术公司，在全息玉米种子生产加工、发挥品种增产优势、提高种子质量方面做了大量工作。尤其是全息种子为农民带来的增产增收效果引起了经销商及广大读者的浓厚兴趣，应广大种子经销商及农民朋友的要求。     

Nanoscale imaging of buried structures via scanning near-field ultrasound holography

A nondestructive imaging method, scanning near-field ultrasound holography (SNFUH), has been developed that provides depth information as well as spatial resolution at the 10- to 100-nanometer scale. In SNFUH, the phase and amplitude of the scattered specimen ultrasound wave, reflected in perturbation to the surface acoustic standing wave, are mapped with a scanning probe microscopy platform to provide nanoscale-resolution images of the internal substructure of diverse materials. We have used SNFUH to image buried nanostructures, to perform subsurface metrology in microelectronic structures, and to image malaria parasites in red blood cells.     

基于光作用的虚拟植物生长模拟与可视化研究

虚拟植物生长模拟研究是数字林业的研究热点。为了在植物生长过程模拟中考虑植物的生理特征,真实地 反映不同光照条件对植物各组织器官形态结构及生长发育特征的影响。基于植物的光生长环境仿真,提出了一种 基于光照模型的植物器官形态结构动态演替生长算法。采用双三次Bezier 曲面构建植物叶片组织器官,并引入曲 面影响因子、植物光属性因子,对植物形态结构和叶序分布进行真实感建模。根据光照对植物叶片生长发育的影 响,提出了基于光作用的碳汇动力学仿真和植物分枝结构的动态演替方法。为了验证本算法的有效性,依据不同 光照条件下绿萝的生理特征数据,对该生长模型算法进行了有效验证,获得了较好的真实感效果。      

美国农业信息化的特点与启示

电脑在农场中普及应用以及支撑精准农业发展的物化信息技术推广的数据显示,信息技术对美国农业生产及经营产生深刻影响。美国颁布了一系列关于信息公开、信息收集与发布和电子政府建设、个人隐私权保护的法律法规,为农业信息化发展提供了制度框架。美国首席信息官委员会(CIOC)和农业部首席信息官办公室(OCIO)的行政主导为农业信息系统互联、兼容和业务协同提供了组织保障。农业网络信息中心联盟(AgNIC)是农业信息资源共建共享的一个范例。农场经济规模是制约信息技术应用的重要因素。美国农业信息化水平居于世界前列,研究其做法及特点…     

不同光照条件对槲蕨组织培养外植体褐化的影响

采用组织培养方法,探讨了黑暗、1 000 lx、2 000 lx和3 000 lx等4种不同光照条件对槲蕨外植体褐变程度的影响.结果表明:随着光照时间的延长,槲蕨外植体的PPO、POD和总酚含量均表现为先增加后减少的趋势:在相同培养时间下,随着光照强度的增加,槲蕨外植体的PPO和POD活性也同时增加,其中光照强度1 000 lx处理的PPO和POD的活性均低于其他光照强度处理;光照对槲蕨外植体的总酚含量在相同培养时间下影响并不直接,但1 000 lx处理下的槲蕨外植体的总酚含量积累较少,说明1 000 lx是槲蕨的组织培养较为适宜的光照条件.     

光强对水稻秧苗素质的影响

本试验以1 000、2 000、4 000、6 000 lx 4种光强处理水稻秧苗,研究光强对秧苗素质的影响,比较分析了水稻的苗高、秧块重量、不定根数、白根数、最长不定根根长等形态指标,以及根系吸收面积、根系活力、叶绿素含量、可溶性糖含量生理指标。结果表明,4 000 lx水平下培育的秧苗素质最高。     

路灯照射对大豆生长发育和产量的影响

通过对淮北市五马路沿线2块夏大豆的田间调查分析表明:受路灯照射的影响,夏大豆株高增加,开花期、成熟期推迟,底荚部位上升,单株生产力下降.且距离越近,植株越高,开花、成熟越晚,底荚部位越高,单株生产力越低.     

弱光照射及保鲜剂对芦笋冷藏品质的影响

采用在普通冷藏环境下引入弱光照射和化学保鲜剂6-BA、壳聚糖处理来延长芦笋的货架期,并考察弱光照射与化学保鲜剂对芦笋冷藏效果的协同作用.弱光光源使用红色发光二极管,6-BA浓度为10 mg/L,壳聚糖浓度为1.5%,定期检测芦笋的感官、失重率、Vc含量、叶绿素含量、可溶性固形物和纤维素含量6个指标.实验结果表明将弱光照射引入到普通冷藏环境,可以较好地改善芦笋的贮藏品质,在贮藏前期还可以增加芦笋的Vc含量、阻止叶绿素的降解、推迟并延长芦笋的后熟期,减缓纤维素含量的增加,但在控制芦笋失水率方面作用不大;6-BA处理和壳聚糖涂膜对芦笋贮藏品质的改善也有积极的作用.本实验期望把弱光照射和化学保鲜剂引入普通冷藏能成为一种新的芦笋保鲜工艺.     

全光照电子喷雾在育苗技术上的应用研究

全光照电子喷雾育苗技术是快速、大量培养扦插苗木的一种很好的方法,我们经过多年的应用研究,总结出了几点育苗生产中应注意的几个关键问题。