Radar glory from buried craters on icy moons

Three ice-covered moons of Jupiter, in comparison with rocky planets and Earth's moon, produce radar echoes of astounding strengths and bizarre polarizations. Scattering from buried craters can explain these and other anomalous properties of the echoes. The role of such craters is analogous to that of the water droplets that create the apparition known as "the glory," the optically bright region surrounding an observer's shadow on a cloud. Both situations involve the electromagnetic phenomenon of total internal reflection at a dielectric interface, operating in a geometry that strongly favors exact backscattering. Dim surface craters are transformed into bright glory holes by being buried under somewhat denser material, thereby increasing the intensity of their echoes by factors of hundreds. The dielectric interface thus formed at the crater walls nicely accounts for the unusual polarizations of the echoes.     

Is GRO J1744-28 a strange star?

The unusual hard x-ray burster GRO J1744-28 recently discovered by the Compton Gamma-Ray Observatory can be modeled as a strange star with a dipolar magnetic field of 相似文献   

Effects of the Large June 1975 Meteoroid Storm on Earth's Ionosphere

The June 1975 meteoroid storm detected on the moon by the Apollo seismometers was the largest ever observed. Reexamination of radio data taken at that time showed that the storm also produced pronounced disturbances on Earth, which were recorded as unique phase anomalies on very low frequency (VLF) radio propagation paths in the low terrestrial ionosphere. Persistent effects were observed for the major storm period (20 to 30 June 1975), including reductions in the diurnal phase variation, advances in the nighttime and daytime phase levels, and reductions in the sunset phase delay rate. Large nighttime phase advances, lasting a few hours, were detected on some days at all VLF transmissions, and for the shorter propagation path they were comparable to solar Lyman alpha daytime ionization. Ion production rates attributable to the meteor storm were estimated to be about 0.6 to 3.0 ions per centimeter cubed per second at the E and D regions, respectively. The storm was a sporadic one with a radiant (that is, the point of apparent origin in the sky) located in the Southern Hemisphere, with a right ascension 1 to 2 hours larger than the sun's right ascension.     

Emplacement of cretaceous-tertiary boundary shocked quartz from chicxulub crater

Observations on shocked quartz in Cretaceous-Tertiary (K-T) boundary sediments compellingly tied to Chicxulub crater raise three problems. First, in North America shocked quartz occurs above the main K-T ejecta layer. Second, shocked quartz is more abundant west than east of Chicxulub. Third, shocked quartz reached distances requiring initial velocities up to 8 kilometers per second, corresponding to shock pressures that would produce melt, not the moderate-pressure shock lamellae observed. Shock devolatilization and the expansion of carbon dioxide and water from impacted wet carbonate, producing a warm, accelerating fireball after the initial hot fireball of silicate vapor, may explain all three problems.     

Bright Spots, Structure, and Magmatism in Southern Tibet from INDEPTH Seismic Reflection Profiling

INDEPTH seismic reflection profiling shows that the decollement beneath which Indian lithosphere underthrusts the Himalaya extends at least 225 kilometers north of the Himalayan deformation front to a depth of approximately 50 kilometers. Prominent reflections appear at depths of 15 to 18 kilometers near where the decollement reflector apparently terminates. These reflections extend north of the Zangbo suture to the Damxung graben of the Tibet Plateau. Some of these reflections have locally anomalous amplitudes (bright spots) and coincident negative polarities implying that they are produced by fluids in the crust. The presence of geothermal activity and high heat flow in the regions of these reflections and the tectonic setting suggest that the bright spots mark granitic magmas derived by partial melting of the tectonically thickened crust.     

柑桔实蝇幼虫振动信号的初步研究

对柑桔果实内两种实蝇幼虫的振动信号研究表明,蜜柑大实蝇(Te-tradacus tsunenonis Miyake)以单头幼虫为害,幼虫取食的振动信号频率较高,持续时间较长,容易辨识;桔大实蝇(T.citri Chen)以多头幼虫为害,不同个体的活动导致振动信号的混合和迭加,信号波型变化很大,采用常规示波技术难以进行定性定量分析。作者还讨论了本研究所用仪器的灵敏度和利用幼虫振动信号检测果实的可能性。     

大黄鱼的发声及信号特性研究

对大黄鱼Pseudosciaena crocea觅食及产卵时的发声及信号特性进行了研究。结果表明:不同行为下大黄鱼发声信号的频谱特性一致,即约在800 Hz频率处有一个明显的谱峰;但不同行为下发声的时域信号差距较大,即觅食时大黄鱼的发声信号都是简单的单脉冲,脉冲间隔大多集中在1~30 ms,脉冲间隔比较小,而产卵时大黄鱼的发声信号则大部分是连续的双脉冲或三脉冲,只有极个别的单脉冲或多脉冲,脉冲间隔则集中在100~130 ms,脉冲间隔要大得多。     

Sound Playback Experiments with Southern Right Whales (Eubalaena australis)

A variety of sound recordings were played to southern right whales. Whales approached the loudspeaker and made frequent sounds in response to recordings of other southern right whales, but swam away and made relatively few sounds in response to playbacks of water noise, 200-hertz tones, and humpback whale sounds. Thus it appears that southern right whales can differentiate between con-specific sounds and other sounds.     

Neural attenuation of responses to emitted sounds in echolocating rats

Bats of the family Vespertilionidae enmit strong ultrasonic pulses for echolocation. If such sounds directly stimulate their ears, the detection of echoes from short distances would be impaired. The responses of lateral lemniscal neurons to emitted sounds were found to be much smaller than those to playback sounds, even when the response of the auditory nerve was the same to both types of sounds. Thus, responses to self-vocalized sounds were attenuated between the cochlear nerve and the inferior colliculus. The mean attenuation was 25 decibels. This neural attenuating mechanism is probably a part of the mechanisms for effective echo detection.     

Songs of humpback whales

1) Humpback whales (Megaptera novaeangliae) produce a series of beautiful and varied sounds for a period of 7 to 30 minutes and then repeat the same series with considerable precision. We call such a performance "singing" and each repeated series of sounds a "song." 2) All prolonged sound patterns (recorded so far) of this species are in song form, and each individual adheres to its own song type. 3) There seem to be several song types around which whales construct their songs, but individual variations are pronounced (there is only a very rough species-specific song pattern). 4) Songs are repeated without any obvious pause between them; thus song sessions may continue for several hours. 5) The sequence of themes in successive songs by the same individual is the same. Although the number of phrases per theme varies, no theme is ever completely omitted in our sample. 6) Loud sounds in the ocean, for example dynamite blasts, do not seem to affect the whale's songs. 7) The sex of the performer of any of the songs we have studied is unknown. 8) The function of the songs is unknown.     

Dynamics of the vocal imitation process: how a zebra finch learns its song

Song imitation in birds provides good material for studying the basic biology of vocal learning. Techniques were developed for inducing the rapid onset of song imitation in young zebra finches and for tracking trajectories of vocal change over a 7-week period until a match to a model song was achieved. Exposure to a model song induced the prompt generation of repeated structured sounds (prototypes) followed by a slow transition from repetitive to serial delivery of syllables. Tracking this transition revealed two phenomena: (i) Imitations of dissimilar sounds can emerge from successive renditions of the same prototype, and (ii) developmental trajectories for some sounds followed paths of increasing acoustic mismatch until an abrupt correction occurred by period doubling. These dynamics are likely to reflect underlying neural and articulatory constraints on the production and imitation of sounds.     

红观音姜荷花新品种的选育及栽培技术

姜荷花原产泰国,由于花形奇特、花期长、耐热性强而受到欢迎,但其花色粉红、颜色较淡。在泰国引进 姜荷花并进行推广的过程中,发现了颜色深红的姜荷花突变株,通过组培快繁获得了大量种苗并于2005要2011 年 间种植,表现出稳定性状。2011 年1 月,该品种通过了广东省农作物品种审定并命名为红观音姜荷花。红观音姜荷花 与亲本相比,具有更高的观赏价值,适合我国华南地区露地作为切花栽培。     

Terrestrial carbon and nitrogen isotopic ratios from cretaceous-tertiary boundary nanodiamonds

One hypothesis for the origin of the nanometer-size diamonds found at the Cretaceous-Tertiary (K-T) boundary is that they are relict interstellar diamond grains carried by a postulated asteroid. The (13)C/(12)C and (15)N/(14)N ratios of the diamonds from two sites in North America, however, show that the diamonds are two component mixtures differing in carbon and nitrogen isotopic composition and nitrogen abundance. Samples from a site from Italy show no evidence for either diamond component. All the isotopic signatures obtained from the K-T boundary are material well distinguished from known meteoritic diamonds, particularly the fine-grain interstellar diamonds that are abundant in primitive chondrites. The K-T diamonds were most likely produced during the impact of the asteroid with Earth or in a plasma resulting from the associated fireball.     

Simultaneous generalization gradients for appetitive and aversive behavior

In the presence of a bright light five monkeys were trained to press a lever to avoid shock and to pull a chain for food reward. When tested with a series of lights dimmer than the conditioning stimulus, the monkeys showed a sharp gradient of effect for the rewarded response, in contrast to a very flat gradient for the avoidance response.     

计量经济学及其在农业中的应用

本文论述计量经济学的特点、方法以及在农业中的应用,提出建立计量分析的函数式所需做的实验计划。最后,根据我国横断面农业资料,以最小二乘法导出了宏观生产函数。     

Early optical polarization of a gamma-ray burst afterglow

We report the optical polarization of a gamma-ray burst (GRB) afterglow, obtained 203 seconds after the initial burst of gamma-rays from GRB 060418, using a ring polarimeter on the robotic Liverpool Telescope. Our robust (2sigma) upper limit on the percentage of polarization, less than 8%, coincides with the fireball deceleration time at the onset of the afterglow. The combination of the rate of decay of the optical brightness and the low polarization at this critical time constrains standard models of GRB ejecta, ruling out the presence of a large-scale ordered magnetic field in the emitting region.     

产PUFAs菌株诱变育种研究进展

多不饱和脂肪酸（PUFAS）对人体健康有重要意义,利用真菌发酵生产多不饱和脂肪酸前景广阔。该研究着重论述了利用不同诱变方法来产生PUFAS领域取得的最新进展,以及诱变中用常用的筛选方法。     

White light sunspot observations from the solar optical universal polarimeter on spacelab-2

The flight of the Solar Optical Universal Polarimeter on Spacelab-2 provided the opportunity for the collection of time sequences of diffraction-limited (0.5 are second) solar images with excellent pointing stability (0.003 are second) and with freedom from the distortion that plagues ground-based images. A series of white-light images of active region 4682 were obtained on 5 August 1985, and the area containing the sunspot has been analyzed. These data have been digitally processed to remove noise and to separate waves from low-velocity material motions. The results include (i) proper motion measurements of a radial outflow in the photospheric granulation pattern just outside the penumbra; (ii) discovery of occasional bright structures ("streakers") that appear to be ejected outward from the penumbra; (iii) broad dark "clouds" moving outward in the penumbra, in addition to the well-known bright penumbral grains moving inward; (iv) apparent extensions and contractions of penumbral filaments over the photosphere; and (v) observation of a faint bubble or looplike structure that seems to expand from two bright penumbral filaments into the photosphere.     

具抗植物病原真菌活性海洋霉菌的筛选与鉴定

以8种植物病原真菌为指示菌,采用双向培养法对渤海海水中分离到的127株霉菌进行抗菌活性初筛,获得了具有不同抗菌谱的菌株41株。采用滤纸片法对其发酵液进行复筛,发现67#菌株不但抗菌谱广,而且抗菌活性极其明显,具有良好的开发前景。对该菌株进行鉴定,确定它属于青霉属(PenicilliumLK.ex Fries)微生物。