Arcs and Clumps in the Uranian lgr Ring

Careful reprocessing of the Voyager images reveals that the Uranìan lambda ring has marked longitudinal variations in brightness comparable in magnitude to those in Saturn's F ring and Neptune's Adams ring. The ring's variations show a dominant five-cycle (72-degree) periodicity, although additional structure down to scales of about 0.5 degree is also present. The ring's shape is defined by a small overall eccentricity plus a six-cycle (60-degree) sinusoidal variation of radial amplitude around 4 kilometers. Both of these properties can be explained by the resonant perturbations of a moon at a semimajor axis of 56,479 kilometers, but no known moon orbits at this location. Unfortunately, the mass required suggests that such a body should have been imaged by Voyager.     

Neptune's Story

It is conjectured that Triton was captured from a heliocentric orbit as the result of a collision with what was then one of Neptune's regular satellites. The immediate post-capture orbit was highly eccentric with a semimajor axis a approximately 10(3)R(N) and a periapse distance rp that oscillated periodically above a minimum value of about 5R(N). Dissipation due to tides raised by Neptune in Triton caused Triton's orbit to evolve to its present state in less, similar10(9) years. For much of this time Triton was almost entirely molten. While its orbit was evolving, Triton cannibalized most of the regular satellites of Neptune and also perturbed Nereid, thus accounting for that satellite's highly eccentric and inclined orbit. The only regular satellites of Neptune that survived were those that formed well within 5R(N) and they move on inclined orbits as the result of chaotic perturbations forced by Triton. Neptune's arcs are confined around the corotation resonances of one of these inner satellites. The widths and lengths of the arcs imply that the satellite's radius is at least 30/(sin i)(2/3) kilometers for i less, similar 1, where i is the angle of inclination.     

An Explanation for Earth's Long-Term Rotational Stability

Paleomagnetic data show less than approximately 1000 kilometers of motion between the paleomagnetic and hotspot reference frames-that is, true polar wander-during the past 100 million years, which implies that Earth's rotation axis has been very stable. This long-term rotational stability can be explained by the slow rate of change in the large-scale pattern of plate tectonic motions during Cenozoic and late Mesozoic time, provided that subducted lithosphere is a major component of the mantle density heterogeneity generated by convection. Therefore, it is unnecessary to invoke other mechanisms, such as sluggish readjustment of the rotational bulge, to explain the observed low rate of true polar wander.     

An Explanation for Symmetry-Induced Isotopic Fractionation in Ozone

Application of a theory of nuclear symmetry-based reaction restrictions to the O2 + O --> O3 reaction provides a potential explanation for the symmetry-induced isotopic enrichment observed for laboratory and atmospherically produced O3. Within this theory, the rate of formation of O3 from collisions of O and isotopically homonuclear O2 depends on whether the O2 molecule is in an f (allowed) or an e (restricted) parity label state. The restriction can be relaxed by various potential energy surface coupling terms, and the assumption that approximately 78 percent of the restricted O2(e) levels produce O3 with the same efficiency as the allowed O2(f) levels can account for laboratory-observed isotopic fractionation. In particular, the theory explains the special enhanced formation of the completely asymmetric isotopomer 16O17O18O.     

Hot Plasma and Energetic Particles in Neptune's Magnetosphere

The low-energy charged particle (LECP) instrument on Voyager 2 measured within the magnetosphere of Neptune energetic electrons (22 kiloelectron volts /=0.5 MeV per nucleon) energies, using an array of solid-state detectors in various configurations. The results obtained so far may be summarized as follows: (i) A variety of intensity, spectral, and anisotropy features suggest that the satellite Triton is important in controlling the outer regions of the Neptunian magnetosphere. These features include the absence of higher energy (>/=150 keV) ions or electrons outside 14.4 R(N) (where R(N) = radius of Neptune), a relative peak in the spectral index of low-energy electrons at Triton's radial distance, and a change of the proton spectrum from a power law with gamma >/= 3.8 outside, to a hot Maxwellian (kT [unknown] 55 keV) inside the satellite's orbit. (ii) Intensities decrease sharply at all energies near the time of closest approach, the decreases being most extended in time at the highest energies, reminiscent of a spacecraft's traversal of Earth's polar regions at low altitudes; simultaneously, several spikes of spectrally soft electrons and protons were seen (power input approximately 5 x 10(-4) ergs cm(-2) s(-1)) suggestive of auroral processes at Neptune. (iii) Composition measurements revealed the presence of H, H(2), and He(4), with relative abundances of 1300:1:0.1, suggesting a Neptunian ionospheric source for the trapped particle population. (iv) Plasma pressures at E >/= 28 keV are maximum at the magnetic equator with beta approximately 0.2, suggestive of a relatively empty magnetosphere, similar to that of Uranus. (v) A potential signature of satellite 1989N1 was seen, both inbound and outbound; other possible signatures of the moons and rings are evident in the data but cannot be positively identified in the absence of an accurate magnetic-field model close to the planet. Other results indude the absence of upstream ion increases or energetic neutrals [particle intensity (j) < 2.8 x 10(-3) cm(-2) s(-1) keV(-1) near 35 keV, at approximately 40 R(N)] implying an upper limit to the volume-averaged atomic H density at R 22 keV) input on Neptune is approximately 3 x 10(7) W, surprisingly small when compared to energy input into the atmosphere of Jupiter, Saturn, and Uranus.     

An Explanation of the Liesegang Phenomenon

Periodic band precipitation in porous media is explained by means of the Hirsch effect (specific semipermeability of the precipitate occurring only as long as both the precipitate-forming ions are present). The possibility of getting Liesegang bands in immunological precipitates is underlined, and a suggestion is made how to avoid them.     

Simple Dynamical Models of Neptune's Great Dark Spot

The large amplitude oscillations of the shape of Neptune's Great Dark Spot are well reproduced by simple dynamical models of an isolated vortex embedded in a background shear flow. From the time series of the aspect ratio and inclination of the vortex values are estimated for the background shear and the mean vorticity of the Great Dark Spot, and a lower bound is placed on the value of the Rossby deformation radius. These models imply the existence of a planetary-scale zone of deterministic chaotic advection in the atmosphere of Neptune.     

Neptune's eccentricity and the nature of the kuiper belt

The small eccentricity of Neptune may be a direct consequence of apsidal wave interaction with the trans-Neptune population of debris called the Kuiper belt. The Kuiper belt is subject to resonant perturbations from Neptune, so that the transport of angular momentum by density waves can result in orbital evolution of Neptune as well as changes in the structure of the Kuiper belt. In particular, for a belt eroded out to the vicinity of Neptune's 2:1 resonance at about 48 astronomical units, Neptune's eccentricity can damp to its current value over the age of the solar system if the belt contains slightly more than an earth mass of material out to about 75 astronomical units.     

Neptune's partial rings: action of galatea on self-gravitating arc particles

Numerical simulations of Neptune's arcs show that self-gravity between macroscopic arc particles can prevent interparticle impacts and thereby stabilize their resonant confinement by Galatea, a satellite of Neptune. Stable subkilometer arc particles provide a source for replenishing the observed dust and explain the clumpy substructure seen in arcs. A few confining kilometer-sized particles between the major arc components can account for the observed arc widths spanning several resonance sites. The modeled distribution of dust is consistent with observations and helps to explain how embedded satellites may affect the structure and evolution of planetary ring systems.     

Neptune's Wind Speeds Obtained by Tracking Clouds in Voyager Images

Images of Neptune obtained by the narrow-angle camera of the Voyager 2 spacecraft reveal large-scale cloud features that persist for several months or longer. The features' periods of rotation about the planetary axis range from 15.8 to 18.4 hours. The atmosphere equatorward of -53 degrees rotates with periods longer than the 16.05-hour period deduced from Voyager's planetary radio astronomy experiment (presumably the planet's internal rotation period). The wind speeds computed with respect to this radio period range from 20 meters per second eastward to 325 meters per second westward. Thus, the cloud-top wind speeds are roughly the same for all the planets ranging from Venus to Neptune, even though the solar energy inputs to the atmospheres vary by a factor of 1000.     

Hubble Space Telescope Imaging of Neptune's Cloud Structure in 1994

Images of Neptune taken at six wavelengths with the Hubble Space Telescope in October and November 1994 revealed several atmospheric features not present at the time of the Voyager spacecraft encounter in 1989. Furthermore, the largest feature seen in 1989, the Great Dark Spot, was gone. A dark spot of comparable size had appeared in the northern hemisphere, accompanied by discrete bright features at methane-band wavelengths. At visible wavelengths, Neptune's banded structure appeared similar to that seen in 1989.     

《四库全书总目·茶经》疏证

本文对《四库全书总目》之《茶经》条作出疏证:对《四库全书·茶经》的分类进行简单辨析;对陆羽生平和《茶经》的成书过程作简要介绍,对提要所及陆羽所授官职和时间进行订正;考证《四库全书·茶经》的版本;详述七之事可以旁资考辨的条目;补充《茶经》的意义与影响。     

A 6-GeV Storage Ring: An Advanced Photon Research Facility

The high brightness of synchrotron radiation produced by storage rings has enhanced research capability by factors of 10(6) to 10(8), from the ultraviolet to the x-ray region. There has been a steady growth in synchrotron radiation research of interest in physics, chemistry, biology, geology, and the other physical sciences and their associated technologies. A large number of university, government, and industrial research organizations are utilizing this new capability at existing facilities. In the process, new partnerships have been created among these communities that have enabled each to contribute its expertise and to obtain its needed capability. A 6-gigaelectron volt storage ring, designed for use with periodic magnetic insertion devices called wigglers and undulators, has been proposed; such a facility could provide further enhancements of 10(4) to 10(6) in capability and could double the synchrotron radiation research capacity in the United States. This enhanced capability and capacity will provide new opportunities for a broad range of scientific and technological interests.     

证券市场"异象"的行为金融学解释及评介

通过对行为金融学领域有关过度反应和反应不足的四大理论模型,即BSV,DHS,HS和BHS的分析和评介,从投资者的认知偏差和投资行为的非理性角度诠释了证券市场异常行为产生的原因,并从投资者的角度提出基于上述异象的投资策略和建议。     

五色草的栽培与应用

本文通过对五色草的栽培研究、观察，掌握其在本地区自然条件下的物候、生态习性，繁殖和越冬技术，在城市绿化建设中得到广泛应用。     

混流式水轮机座环过渡段的结构分析

通过对混流式水轮机座环过渡段进行分析,获得了过渡段的最优结构。分析结果用C语言编写了程序,应用此程序可以提高设计精度,优化结构,缩短设计周期。