脉冲掺铒波导激光器研究进展

目前发展的用于脉冲掺铒光波导激光器的技术主要有：调Q技术、半导体饱和吸收镜被动锁模技术以及带尾纤的碳纳米管（CNTs）饱和吸收被动锁模技术。对基于调Q技术的波导嫩光器、基于半导体饱和吸收镜被动锁模技术的波导激光器、带尾纤的碳纳米管（CNTs）饱和吸收被动锁模技术的波导激光器的发展现状以及存在的问题进行了分析研究,并针对目前存在的问题,指出了其发展方向。     

物流系统中运输方式的选择

采用权重系数变换法将运输方式多目标选择优化问题转化为单目标优化问题,提出了以时间、费用整体综合效益最优来完成运输任务的运输方式选择模型;并结合改进的遗传算法分析了模型的求解过程.通过合理的编码方法和遗传算子,能够方便、快速地进行计算,有助于物流运输者选择经济、合理的运输方式.     

Hyperacuity in cat retinal ganglion cells

Cat X retinal ganglion cells that can resolve sine gratings of only 2.5 cycles per degree can nevertheless respond reliably to displacements of a grating of approximately 1 minute of arc. This is a form of hyperacuity comparable in magnitude to that seen in human vision. A theoretical analysis of this form of hyperacuity reveals it to be a result of the high gain and low noise of ganglion cells. The hyperacuity expected for the best retinal ganglion cells is substantially better than that observed in behavioral experiments. Thus the brain, rather than improving on the retinal signal-to-noise ratio by pooling signals from many ganglion cells, is unable to make use of all the hyperacuity information present in single ganglion cell responses.     

Light adaptation in cat retinal rods

It has long been an open question whether individual rod receptors in the mammalian retina show any light adaptation. The prevailing evidence so far has suggested that these cells, unlike those in lower vertebrates, adapt little if at all. The experiments on cat rods reported here, however, indicate that this is not really true. Since the cone system in the cat retina has a fairly high light threshold, the rods also need to adapt so that they do not saturate with light before the cones fully take over vision at higher light intensities. In similar experiments, adaptation was found in rods of other mammalian species, including primates.     

Blood velocity measurements in human retinal vessels

Laser Doppler velocimetry was used to measure the velocity of blood in human retinal vessels. The mean flow velocities obtained were 1.9 centimeters per second in a retinal vein and 2.2 centimeters per second in a retinal artery. Scattered light from a weak helium-neon laser beam focused on the vessel was detected by a photomultiplier, and the temporal correlation of the intensity fluctuations was measured with a photon counting autocorrelator. Autocorrelation functions for blood flowing through glass capillaries were used for calibration.     

Unusual retinal cells in the dolphin eye

By comparison to the cellular constituents of the retinas of certain other diving mammals, the elements of the dolphin retina include an unusually large number of specialized cells. Both cone and rod receptors may be identified. An unusual amacrine cell may be seen which produces a process that spans the cells between the inner plexiform and outer plexiform layers. Most unusual is a layer of giant ganglion cells which appears to serve most of the central retina. The giant ganglion cells support giant dendrites and optic nerve fibers which range up to 8 micrometers in diameter.     

Coherent control of retinal isomerization in bacteriorhodopsin

Optical control of the primary step of photoisomerization of the retinal molecule in bacteriorhodopsin from the all-trans to the 13-cis state was demonstrated under weak field conditions (where only 1 of 300 retinal molecules absorbs a photon during the excitation cycle) that are relevant to understanding biological processes. By modulating the phases and amplitudes of the spectral components in the photoexcitation pulse, we showed that the absolute quantity of 13-cis retinal formed upon excitation can be enhanced or suppressed by +/-20% of the yield observed using a short transform-limited pulse having the same actinic energy. The shaped pulses were shown to be phase-sensitive at intensities too low to access different higher electronic states, and so these pulses apparently steer the isomerization through constructive and destructive interference effects, a mechanism supported by observed signatures of vibrational coherence. These results show that the wave properties of matter can be observed and even manipulated in a system as large and complex as a protein.     

双季稻栽培搭配方式的探讨

以早稻金早47和晚稻天优华占为材料,采用不同的栽培技术(旱育移栽、半旱育移栽、直播、抛秧和机插),研究早晚稻种植最佳的栽培搭配方式。结果表明,金早47产量表现,旱育秧抛秧直播机插,天优华占产量表现,半旱育秧旱育秧抛秧机插;不同栽培方式之间搭配,以早稻旱育秧+晚稻半旱育秧产量水平最高,早稻旱育+秧晚稻旱育秧排在第2位,早稻机插+晚稻机插产量最低。     

贵州旅游产业发展模式剖析

无论从理论到实践，贵州省旅游产业发展模式均不够明朗，亟待理性地加以揭示。通过对比与实证研究表明。贵州旅游产业发展表现为：不完善的政府主导条件下的高速低效扩张的现状特征，以县城为主的旅游产业发展中的政府主导存在多样化模式。宏观上，贵州省旅游产业应在加强政府主导的战略下，实施超前的推进型发展模式，为实施这一战略，应建立包括管理体制、“三区联动”、旅游科教化、强化大旅游意识、多渠道投资、加强产品体系建设、精品战略及全面市场整合等内容的扶持体系。     

江苏省稻米产业化经营的主要组织模式及其分析

江苏省是我国水稻产业化经营最活跃和规模最大的地区之一。通过对江苏省稻米产业化经营发展情况的调研,总结出当前江苏省稻米产业化经营中的4类主要组织模式,即：“企业＋农户”、“企业＋X（第三方）＋农户”、“专业市场＋农户”和“企业与基地一体化”,比较分析了各种模式的运行机制和应用条件,提出“企业＋合作社（或协会）＋农户”模式是值得大力推广的稻米产业化经营的组织模式。     

Candidate taste receptors in Drosophila

Little is known about the molecular mechanisms of taste perception in animals, particularly the initial events of taste signaling. A large and diverse family of seven transmembrane domain proteins was identified from the Drosophila genome database with a computer algorithm that identifies proteins on the basis of structure. Eighteen of 19 genes examined were expressed in the Drosophila labellum, a gustatory organ of the proboscis. Expression was not detected in a variety of other tissues. The genes were not expressed in the labellum of a Drosophila mutant, pox-neuro70, in which taste neurons are eliminated. Tissue specificity of expression of these genes, along with their structural similarity, supports the possibility that the family encodes a large and divergent family of taste receptors.     

Quantum-well states as fabry-Perot modes in a thin-film electron interferometer

Angle-resolved photoemission from atomically uniform silver films on iron (100) shows quantum-well states for absolutely determined film thicknesses ranging from 1 to approximately 100 monolayers. These states can be understood in terms of Fabry-Perot modes in an electron interferometer. A quantitative line shape analysis over the entire two orders of magnitude of thickness range yields an accurate measurement of the band structure, quasiparticle lifetime, electron reflectivity, and phase shift. Effects of confinement energy gap, reflection loss, and surface scattering caused by controlled roughness are demonstrated.