Dark auroral oval on saturn discovered in hubble space telescope ultraviolet images

Hubble Space Telescope ultraviolet images of Saturn obtained with the Faint Object Camera near 220 nanometers reveal a dark oval encircling the north magnetic pole of the planet. The opacity has an equivalent width of approximately 11 degrees in latitude and is centered around approximately 79 degrees N. The oval shape of the dark structure and its coincidence with the aurora detected by the Voyager Ultraviolet Spectrometer suggest that the aerosol formation is related to the auroral activity.     

Hubble space telescope imaging of the north polar aurora on jupiter

The first direct images of the Jovian aurora at ultraviolet wavelengths were obtained by the Hubble Space Telescope Faint Object Camera near the time of the Ulysses spacecraft encounter with Jupiter on 8 February 1992. The auroral oval is not uniformly luminous. It exhibits a brightness minimum in the vicinity of longitude 180 degrees . In the few images available, the brightest part of the oval occurs in late afternoon Jovian time. The observed oval is not concentric with calculated ovals in the O(6) model of Connerney. The size of the oval is consistent with auroral particles on field lines with magnetic L parameter >8, indicating significant migration from lo, its torus, or both, if these are their origins.     

Pioneer 10 observations of the ultraviolet glow in the vicinity of jupiter

A two-channel ultraviolet photometer aboard Pioneer 10 has made several observations of the ultraviolet glow in the wavelength range from 170 to 1400 angstroms in the vicinity of Jupiter. Preliminary results indicate a Jovian hydrogen (1216 angstrom) glow with a brightness of about 1000 rayleighs and a helium (584 angstrom) glow with a brightness of about 10 to 20 rayleighs. In addition, Jupiter appears to have an extensive hydrogen torus surrounding it in the orbital plane of Io. The mean diameter of the torus is about equal to the diameter of the orbit of Io. Several observations of the Galilean satellites have also occurred but only a rather striking Io observation has been analyzed to date. If the observed Io glow is predominantly that of Lyman-alpha, the surface brightness is about 10,000 rayleighs.     

Incipient space weathering observed on the surface of Itokawa dust particles

The reflectance spectra of the most abundant meteorites, ordinary chondrites, are different from those of the abundant S-type (mnemonic for siliceous) asteroids. This discrepancy has been thought to be due to space weathering, which is an alteration of the surfaces of airless bodies exposed to the space environment. Here we report evidence of space weathering on particles returned from the S-type asteroid 25143 Itokawa by the Hayabusa spacecraft. Surface modification was found in 5 out of 10 particles, which varies depending on mineral species. Sulfur-bearing Fe-rich nanoparticles exist in a thin (5 to 15 nanometers) surface layer on olivine, low-Ca pyroxene, and plagioclase, which is suggestive of vapor deposition. Sulfur-free Fe-rich nanoparticles exist deeper inside (<60 nanometers) ferromagnesian silicates. Their texture suggests formation by metamictization and in situ reduction of Fe(2+).     

A silent slip event on the deeper Cascadia subduction interface

Continuous Global Positioning System sites in southwestern British Columbia, Canada, and northwestern Washington state, USA, have been moving landward as a result of the locked state of the Cascadia subduction fault offshore. In the summer of 1999, a cluster of seven sites briefly reversed their direction of motion. No seismicity was associated with this event. The sudden displacements are best explained by approximately 2 centimeters of aseismic slip over a 50-kilometer-by-300-kilometer area on the subduction interface downdip from the seismogenic zone, a rupture equivalent to an earthquake of moment magnitude 6.7. This provides evidence that slip of the hotter, plastic part of the subduction interface, and hence stress loading of the megathrust earthquake zone, can occur in discrete pulses.     

Contact photomicrography in the ultraviolet on high-resolution plates

Ultraviolet photographs of cells can be made without quartz optics by placing the cells on high-resolution plates capable of resolving more than 2000 lines per millimeter and by passing monochromatic radiation of the desired wavelength through them to the emulsion. Prints can be made by enlarging the resulting negative with a microscope to the magnification desired.     

基于时间和空间差异的事件性景观服务设施设计研究——以河北省第二届园林博览会为例

目的事件性景观已成为推动城市更新与发展的有效途径。大型城市事件都有一个从蓄积到发生再到结束后产生效应的全过程,因此其使用人群在事件的发生期和结束后呈现出明显的数量和结构变化,服务设施也相应地出现供需不平衡、景观同质化等问题,因而有必要对事件性景观服务设施的设计提出更为集约和弹性的策略与方法。方法采用基于时间差异的服务设施数量测算方法,该方法包括:(1)在事件发生期,基于瞬时最大游人容量进行服务设施数量测算;(2)在事件结束后,基于城市公共绿地设计规范进行服务设施数量测算。并结合河北省第二届园林博览会的景观服务设施设计,确定两种计算结果,并对其进行分析。结果基于瞬时最大游人容量的测算结果数值较大,基于城市公共绿地设计规范的测算结果数值较小,两者之间存在明显差值。因此,本文建议将事件结束后的服务设施设置为永久性设施,其与事件发生期的差值部分设置为临时性设施,并采用二者相结合的设计策略,提出基于空间差异的场地布局,以满足使用人群的需求变化。结论本文分析了事件性景观服务设施所存在的问题,并根据测算和研究结果提出了基于时间和空间差异的设计策略与方法,以期为同类设计提供有益参考。      

A neural map of auditory space in the owl

Auditory units that responded to sound only when it originated from a limited area of space were found in the lateral and anterior portions of the midbrain auditory nucleus of the owl (Tyto alba). The areas of space to which these units responded (their receptive fields) were largely independent of the nature and intensity of the sound stimulus. The units were arranged systematically within the midbrain auditory nucleus according to the relative locations of their receptive fields, thus creating a physiological map of auditory space.     

紫外光谱法测定发酵液中的透明质酸

利用透明质酸在196 nm波长紫外光下有吸收峰,并且透明质酸在0～1.0 g/L的质量浓度范围内与吸光度有良好的线性关系,采用紫外光谱法测定了发酵法生产透明质酸发酵液中透明质酸的浓度.结果表明,发酵液中透明质酸质量浓度为0.98 g/L,平均回收率为100.45%,相对标准偏差为0.78%,认为紫外光谱法是一种可准确测定透明质酸浓度的方法.     

木兰围场国家森林公园鸟类群落垂直空间格局研究

运用聚类分析（最远距离法）和主分量分析,研究了木兰围场国家森林公园鸟类群落垂直空间格局,根据鸟类的栖息取食行为格局将其分为６个栖息取食集团：地面杂食性鸟类集团,树枝层杂食性鸟类集团,树枝层其它肉食性鸟类集团,树干层食虫鸟类集团,树枝层外层食虫鸟类集团和树枝层内层食虫鸟类集团。     

Isotropic events observed with a borehole array in the Chelungpu fault zone, Taiwan

Shear failure is the dominant mode of earthquake-causing rock failure along faults. High fluid pressure can also potentially induce rock failure by opening cavities and cracks, but an active example of this process has not been directly observed in a fault zone. Using borehole array data collected along the low-stress Chelungpu fault zone, Taiwan, we observed several small seismic events (I-type events) in a fluid-rich permeable zone directly below the impermeable slip zone of the 1999 moment magnitude 7.6 Chi-Chi earthquake. Modeling of the events suggests an isotropic, nonshear source mechanism likely associated with natural hydraulic fractures. These seismic events may be associated with the formation of veins and other fluid features often observed in rocks surrounding fault zones and may be similar to artificially induced hydraulic fracturing.     

Resolving the structure of ionized helium in the intergalactic medium with the far ultraviolet spectroscopic explorer

The neutral hydrogen (H I) and ionized helium (He II) absorption in the spectra of quasars are unique probes of structure in the early universe. We present Far-Ultraviolet Spectroscopic Explorer observations of the line of sight to the quasar HE2347-4342 in the 1000 to 1187 angstrom band at a resolving power of 15,000. We resolve the He II Lyman alpha (Lyalpha) absorption as a discrete forest of absorption lines in the redshift range 2.3 to 2.7. About 50 percent of these features have H I counterparts with column densities N(H I) > 10(12.3) per square centimeter that account for most of the observed opacity in He II Lyalpha. The He II to H I column density ratio ranges from 1 to >1000, with an average of approximately 80. Ratios of <100 are consistent with photoionization of the absorbing gas by a hard ionizing spectrum resulting from the integrated light of quasars, but ratios of >100 in many locations indicate additional contributions from starburst galaxies or heavily filtered quasar radiation. The presence of He II Lyalpha absorbers with no H I counterparts indicates that structure is present even in low-density regions, consistent with theoretical predictions of structure formation through gravitational instability.     

A major Archean,gold- and crust-forming event in the Kaapvaal craton,South Africa

The 2.89- to 2.76-gigayear-old conglomerates of the Central Rand Group of South Africa host an immense concentration of gold. The gold and rounded pyrites from the conglomerates yield a rhenium-osmium isochron age of 3.03 +/- 0.02 gigayears and an initial 187Os/188Os ratio of 0.1079 +/- 0.0001. This age is older than that of the conglomerates. Thus, the gold is detrital and was not deposited by later hydrothermal fluids. This Middle Archean gold mineralization event corresponds to a period of rapid crustal growth in which much of the Kaapvaal craton was formed and is evidence for a significant noble metal flux from the mantle.