Photonic band gap guidance in optical fibers

A fundamentally different type of optical waveguide structure is demonstrated, in which light is confined to the vicinity of a low-index region by a two-dimensional photonic band gap crystal. The waveguide consists of an extra air hole in an otherwise regular honeycomb pattern of holes running down the length of a fine silica glass fiber. Optical fibers based on this waveguide mechanism support guided modes with extraordinary properties.     

Microstructured optical fibers as high-pressure microfluidic reactors

Deposition of semiconductors and metals from chemical precursors onto planar substrates is a well-developed science and technology for microelectronics. Optical fibers are an established platform for both communications technology and fundamental research in photonics. Here, we describe a hybrid technology that integrates key aspects of both engineering disciplines, demonstrating the fabrication of tubes, solid nanowires, coaxial heterojunctions, and longitudinally patterned structures composed of metals, single-crystal semiconductors, and polycrystalline elemental or compound semiconductors within microstructured silica optical fibers. Because the optical fibers are constructed and the functional materials are chemically deposited in distinct and independent steps, the full design flexibilities of both platforms can now be exploited simultaneously for fiber-integrated optoelectronic materials and devices.     

Generation of megawatt optical solitons in hollow-core photonic band-gap fibers

The measured dispersion of a low-loss, hollow-core photonic band-gap fiber is anomalous throughout most of the transmission band, and its variation with wavelength is large compared with that of a conventional step-index fiber. For an air-filled fiber, femtosecond self-frequency--shifted fundamental solitons with peak powers greater than 2megawatts can be supported. For Xe-filled fibers, nonfrequency-shifted temporal solitons with peak powers greater than 5.5 megawatts can be generated, representing an increase in the power that can be propagated in an optical fiber of two orders of magnitude. The results demonstrate a unique capability to deliver high-power pulses in a single spatial mode over distances exceeding 200 meters.     

Attosecond control and measurement: lightwave electronics

Electrons emit light, carry electric current, and bind atoms together to form molecules. Insight into and control of their atomic-scale motion are the key to understanding the functioning of biological systems, developing efficient sources of x-ray light, and speeding up electronics. Capturing and steering this electron motion require attosecond resolution and control, respectively (1 attosecond = 10(-18) seconds). A recent revolution in technology has afforded these capabilities: Controlled light waves can steer electrons inside and around atoms, marking the birth of lightwave electronics. Isolated attosecond pulses, well reproduced and fully characterized, demonstrate the power of the new technology. Controlled few-cycle light waves and synchronized attosecond pulses constitute its key tools. We review the current state of lightwave electronics and highlight some future directions.     

High-speed scanning in human memory

When subjects judge whether a test symbol is contained in a short memorized sequence of symbols, their mean reaction-time increases linearly with the length of the sequence. The linearity and slope of the function imply the existence of an internal serial-comparison process whose average rate is between 25 and 30 symbols per second.     

High-speed chromosome sorting

Dual-beam high-speed sorting has been developed to facilitate purification of chromosomes based on DNA staining with the fluorescent dyes Hoechst 33258 and chromomycin A3. Approximately 200 chromosomes per second of two types can be sorted from a suspension of chromosomes isolated from human lymphoblasts while fluorescent objects (chromosomes, debris fragments, chromosome clumps, and nuclei) are processed at the rate of about 20,000 per second. This sorting rate is approximately ten times that possible with conventional sorters. Chromosomes of a single type can be sorted with a purity of about 90 percent. DNA from the sorted chromosomes is suitable for construction of recombinant DNA libraries and for gene mapping.     

矮牵牛的快速繁殖技术

以矮牵牛为试材,筛选了快速繁殖优良苗木时的最适基本培养基浓度及激素条件．结果表明分化培养时的最适培养基为１／４ ＭＳ＋ ＢＡ０ ．５ ｍｇ／Ｌ＋ＩＢＡ０ ．０２ ｍｇ／Ｌ;增殖培养时为ＭＳ＋ ＢＡ０ ．５ｍｇ／Ｌ＋ ＩＢＡ０ ．２ ｍｇ／Ｌ;诱导根系培养时为１／２ ＭＳ＋ ＩＢＡ０ ．５ ｍｇ／Ｌ＋ 活性炭１００ ｍｇ／Ｌ．生根培养基中添加活性炭有效地促进了矮牵牛根系的生长和发育,同时促进了叶片和茎的分化生长．     

Sodium current in ventricular myocardial fibers

Membrane currents were measured in thin bundles of dog ventricular myocardium under voltage-clamp conditions. A rather large initial inward current which had an equilibrium potential at about + 55 millivolts could be recorded. When the external sodium concentration was reduced, the equilibrium potential for this current was shifted by the amount predicted theoretically for a current carried solely by sodium ions. The size of the sodium inward current (I(Na)) was largely dependent on the preceding membrane potential. The I(Na) was completely inactivated if the membrane potential was as low as -45 millivolts. Sodium ions are the main carrier of charge during the rapid depolarization phase of the action potential.     

Photonic crystal fibers

Photonic crystal fibers guide light by corralling it within a periodic array of microscopic air holes that run along the entire fiber length. Largely through their ability to overcome the limitations of conventional fiber optics-for example, by permitting low-loss guidance of light in a hollow core-these fibers are proving to have a multitude of important technological and scientific applications spanning many disciplines. The result has been a renaissance of interest in optical fibers and their uses.     

高速机车的振动及噪音分析

以列车运行提速后振动加剧的客观事实为背景,为消除机车车辆的颤振现象以及振动对车体、转向架和悬挂系统产生的较大破坏作用,提高车辆运行的平稳性,减小铁道沿线的噪音污染,在分析机车车辆振动现象的基础上,初步提出了避免制动振动的方法,并利用小波变换对信号进行分解的原理,对小波分析在信号降噪的工程应用进行了探讨。     

High-speed cinematographic evidence for ultrafast feeding in antennariid anglerfishes

Analyses by means of high-speed, light cinematography at 800 and 1000 frames per second have shown that members of the shallow-water anglerfish genus Antennarius are capable of producing an enormous suction pressure for prey capture by means of an extraordinarily rapid expansion of the buccal and opercular cavities. Prey is totally engulfed at speeds considerably greater than those recorded for any other fish. The structural adaptations responsible for this rapid prey engulfment provide anglerfishes with one of the fastest known vertebrate feeding mechanisms.     

草莓试管快繁的研究

本试验对草莓的试管快繁技术进行了研究。结果表明:诱导草莓茎尖分化的最适培养基是MS+BA(6——苄基腺嘌呤)0.1～0.5mg·L~(-1),每30天可繁殖一代,增殖15倍,其中50％可用于生根;草莓生根培养基以不加任何激素的MS为最好,接种7天就可生根,生根率达100％;当根长1cm左右时,将草莓试管苗栽入蛭石中,控制温度和湿度,成活率可达90％以上。     

Sarcomeric oscillations in frog skeletal muscle fibers

Brief asynchronous, small-amplitude, cyclic, longitudinal displacements of the striations of frog skeletal muscle fibers were observed with ordinary light microscopy after application of caffeine and certain quaternary ammonium compounds. With time these oscillations became synchronized and evolved into peristaltic-like movements. The oscillations were influenced by sarcomere length, temperature, external concentration of calcium ions, membrane potential, and disruption of the transverse tubules.     

Velocity and displacement responses in auditory-nerve fibers

With the help of nonsiniusoidal acoustic stimuli, it is demonstrated that most fibers of the auditory nerve respond to both displacement and velocity of the basilar membrane. Except at very high stimulus levels, motion and displacement toward scala tympani produce excitation; motion and displacement toward scala vestibuli produce inhibition. The displacement and velocity responses interact. When both are excitatory or inhibitory, they reinforce each other; when they are of opposite nature, a partial cancellation occurs. The presence of both displacement and velocity responses in the single fibers suggests that outer and inner hair cells of the cochlea interact.     

高铁施工料具管理中引进RFID跟踪技术研究

本文针对高铁区段维修作业施工料具管理难的问题,引入物联网RFID射频识别技术,对进出高铁栅栏的施工料具进行全程监控,防止施工料具遗漏现场的问题发生,增大了铁路运输的安全系数。     

百合试管苗快速繁殖技术的研究

对百合鳞片进行了试管快速繁殖研究．结果表明：外植体取样部位影响百合小鳞茎的增殖率,幼嫩的基部增殖率高,而外部、顶部细胞老化的鳞片增殖率低．百合小鳞茎的形成主要靠不定芽的形成．