Images of asteroid 21 Lutetia: a remnant planetesimal from the early Solar System

Images obtained by the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) cameras onboard the Rosetta spacecraft reveal that asteroid 21 Lutetia has a complex geology and one of the highest asteroid densities measured so far, 3.4 ± 0.3 grams per cubic centimeter. The north pole region is covered by a thick layer of regolith, which is seen to flow in major landslides associated with albedo variation. Its geologically complex surface, ancient surface age, and high density suggest that Lutetia is most likely a primordial planetesimal. This contrasts with smaller asteroids visited by previous spacecraft, which are probably shattered bodies, fragments of larger parents, or reaccumulated rubble piles.     

The surface composition and temperature of asteroid 21 Lutetia as observed by Rosetta/VIRTIS

The Visible, InfraRed, and Thermal Imaging Spectrometer (VIRTIS) on Rosetta obtained hyperspectral images, spectral reflectance maps, and temperature maps of the asteroid 21 Lutetia. No absorption features, of either silicates or hydrated minerals, have been detected across the observed area in the spectral range from 0.4 to 3.5 micrometers. The surface temperature reaches a maximum value of 245 kelvin and correlates well with topographic features. The thermal inertia is in the range from 20 to 30 joules meter(-2) kelvin(-1) second(-0.5), comparable to a lunarlike powdery regolith. Spectral signatures of surface alteration, resulting from space weathering, seem to be missing. Lutetia is likely a remnant of the primordial planetesimal population, unaltered by differentiation processes and composed of chondritic materials of enstatitic or carbonaceous origin, dominated by iron-poor minerals that have not suffered aqueous alteration.     

Magnitude of the 2010 Gulf of Mexico oil leak

To fully understand the environmental and ecological impacts of the Deepwater Horizon disaster, an accurate estimate of the total oil released is required. We used optical plume velocimetry to estimate the velocity of fluids issuing from the damaged well both before and after the collapsed riser pipe was removed. We then calculated the volumetric flow rate under a range of assumptions. With a liquid oil fraction of 0.4, we estimated that the average flow rate from 22 April 2010 to 3 June 2010 was 5.6 × 10(4) ± 21% barrels/day (1.0 × 10(-1) meter(3)/second), excluding secondary leaks. After the riser was removed, the flow was 6.8 × 10(4) ± 19% barrels/day (1.2 × 10(-1) meters(3)/second). Taking into account the oil collected at the seafloor, this suggests that 4.4 × 10(6) ± 20% barrels of oil (7.0 × 10(5) meters(3)) was released into the ocean.     

银杏树干边材液流及水容特性研究

为探明银杏(Ginkgo biloba)枝叶水势、水容特征及其对树干边材液流的调节和影响。利用热扩散式边材液流检测技术、压力室技术等对其树干边材液流、枝叶水势、水容等进行测定。结果表明,春、夏、秋三季银杏树干边材平均液流速率分别为（1.11±0.76）×10^-3、（0.82±0.58）×10^-3、（0.94±0.21）×10^-3 cm·s^-1,三者之间无显著差异。银杏枝条与叶片水势、水容具有相似的“V”型日变化。整个生长季,银杏枝条和叶片平均水势分别为（-1.74±0.24）MPa和（-1.80±0.20）MPa;枝条和叶片水容分别为（0.38±0.02）×10^-3 g·cm^-3·MPa^-1和（5.83±1.9）×10^-3 g·cm^-3·MPa^-1。银杏枝叶水势、水容与树干边材液流速率呈负相关,共同作用和调节其蒸腾耗水,但不同时段其主导因子不同。     

Deep Impact observations by OSIRIS onboard the Rosetta spacecraft

The OSIRIS cameras (optical, spectroscopic, and infrared remote imaging system) onboard the European Space Agency's Rosetta spacecraft observed comet 9P/Tempel 1 for 17 days continuously around the time of NASA's Deep Impact mission. The cyanide-to-water production ratio was slightly enhanced in the impact cloud, compared with that of normal comet activity. Dust particles were flowing outward in the coma at >160 meters per second, accelerated by the gas. The slope of the brightness increase showed a dip about 200 seconds after the impact. Dust Afrho values before and long after the impact confirm the slight decrease of cometary activity. The dust-to-water mass ratio was much larger than 1.     

Estimating the mass of asteroid 253 mathilde from tracking data during the NEAR flyby

The terminal navigation of the Near Earth Asteroid Rendezvous (NEAR) spacecraft during its close flyby of asteroid 253 Mathilde involved coordinated efforts to determine the heliocentric orbits of the spacecraft and Mathilde and then to determine the relative trajectory of the spacecraft with respect to Mathilde. The gravitational perturbation of Mathilde on the passing spacecraft was apparent in the spacecraft tracking data. As a result of the accurate targeting achieved, these data could be used to determine Mathilde's mass as 1.033 (+/- 0.044) x 10(20) grams. Coupled with a volume estimate provided by the NEAR imaging team, this mass suggests a low bulk density for Mathilde of 1.3 grams per cubic centimeter.     

KOI-126: a triply eclipsing hierarchical triple with two low-mass stars

The Kepler spacecraft has been monitoring the light from 150,000 stars in its primary quest to detect transiting exoplanets. Here, we report on the detection of an eclipsing stellar hierarchical triple, identified in the Kepler photometry. KOI-126 [A, (B, C)], is composed of a low-mass binary [masses M(B) = 0.2413 ± 0.0030 solar mass (M(⊙)), M(C) = 0.2127 ± 0.0026 M(⊙); radii R(B) = 0.2543 ± 0.0014 solar radius (R(⊙)), R(C) = 0.2318 ± 0.0013 R(⊙); orbital period P(1) = 1.76713 ± 0.00019 days] on an eccentric orbit about a third star (mass M(A) = 1.347 ± 0.032 M(⊙); radius R(A) = 2.0254 ± 0.0098 R(⊙); period of orbit around the low-mass binary P(2) = 33.9214 ± 0.0013 days; eccentricity of that orbit e(2) = 0.3043 ± 0.0024). The low-mass pair probe the poorly sampled fully convective stellar domain offering a crucial benchmark for theoretical stellar models.     

Pioneer saturn celestial mechanics experiment

During the Pioneer Saturn encounter, a continuous round-trip radio link at S band ( approximately 2.2 gigahertz) was maintained between stations of the Deep Space Network and the spacecraft. From an analysis of the Doppler shift in the radio carrier frequency, it was possible to determine a number of gravitational effects on the trajectory. Gravitational moments ( J(2) and J(4)) for Saturn have been determined from preliminary analysis, and preliminary mass values have been determined for the Saturn satellites Rhea, Iapetus, and Titan. For all three satellites the densities are low, consistent with the compositions of ices. The rings have not been detected in the Doppler data, and hence the best preliminary estimate of their total mass is zero with a standard error of 3 x 10(-6) Saturn mass. New theoretical calculations for the Saturn interior are described which use the latest observational data, including Pioneer Saturn, and state-of-the-art physics for the internal composition. Probably liquid H(2)O and possibly NH(3) and CH(4) are primarily confined in Saturn to the vicinity of a core of approximately 15 to 20 Earth masses. There is a slight indication that helium may likewise be fractionated to the central regions.     

Amalthea's density is less than that of water

Radio Doppler data from the Galileo spacecraft's encounter with Amalthea, one of Jupiter's small inner moons, on 5 November 2002 yield a mass of (2.08 +/- 0.15) x 10(18) kilograms. Images of Amalthea from two Voyager spacecraft in 1979 and Galileo imaging between November 1996 and June 1997 yield a volume of (2.43 +/- 0.22) x 10(6) cubic kilometers. The satellite thus has a density of 857 +/- 99 kilograms per cubic meter. We suggest that Amalthea is porous and composed of water ice, as well as rocky material, and thus formed in a cold region of the solar system, possibly not at its present location near Jupiter.     

NEAR's flyby of 253 mathilde: images of a C asteroid

On 27 June 1997, the Near Earth Asteroid Rendezvous (NEAR) spacecraft flew within 1212 kilometers of asteroid 253 Mathilde. Mathilde is an irregular, heavily cratered body measuring 66 kilometers by 48 kilometers by 46 kilometers. The asteroid's surface is dark (estimated albedo between 0.035 and 0.050) and similar in color to some CM carbonaceous chondrites. No albedo or color variations were detected. The volume derived from the images and the mass from Doppler tracking of the spacecraft yield a mean density of 1.3 +/- 0.2 grams per cubic centimeter, about half that of CM chondrites, indicating a porous interior structure.     

Discovery of mass anomalies on Ganymede

We present the discovery of mass anomalies on Ganymede, Jupiter's third and largest Galilean satellite. This discovery is surprising for such a large icy satellite. We used the radio Doppler data generated with the Galileo spacecraft during its second encounter with Ganymede on 6 September 1996 to model the mass anomalies. Two surface mass anomalies, one a positive mass at high latitude and the other a negative mass at low latitude, can explain the data. There are no obvious geological features that can be identified with the anomalies.     

甘草次酸在Caco-2细胞模型中的转运机制

采用液相-质谱检测甘草次酸在HBSS磷酸盐缓冲液中的转运量,结果表明:甘草次酸的转运量受时间、浓度以及p-糖蛋白抑制剂维拉帕米和汉防己甲素的影响,表观渗透系数P(appBL-AP)为(17.1±4.2) ×10-6～(54.3±6.3) ×10-6cm·s-1、P(appAP-BL)为(15.6-±3.4) ×10-6...     

球孢白僵菌Bb-10-12对苜蓿叶象甲的室内毒力研究

利用孢子浓度为1.65×105～1.65×109个孢子/mL的球孢白僵菌Bb-10-12菌悬液对苜蓿叶象甲幼虫和成虫进行毒力研究。结果表明,该菌株具有较高的杀虫活性,孢子浓度为1.65×108个孢子/mL时,对2龄幼虫最高累计校正死亡率为100%,致死中浓度为1.3959×106个孢子/mL,致死中时间(7.73±2.81)d;对4龄幼虫最高累计校正死亡率为89.29%,致死中浓度为3.3175×106个孢子/mL,致死中时间(9.10±0.28)d;对成虫最高累计校正死亡率为61.11%,致死中浓度为4.8287×108个孢子/mL,致死中时间(27.48±0.15)d。比较可知,该菌株对苜蓿叶象甲2龄幼虫防治效果最好。     

花(♀)×唇(♂)杂交子一代胚胎发育研究

采用人工催产和干法授精技术,在ZOOM645S解剖镜下对花(Hemibarbus maculatus)(♀)×唇(H.labeo)(♂)杂交子一代(F1)胚胎发育过程中各发育时期的发育时序和形态特征进行了观察。结果表明,受精卵为强黏性卵,卵径为1.60～1.80 mm。在孵化水温为(20±1)℃条件下,受精后1 h胚盘隆起;1 h20 min进入卵裂期;6 h 20 min进入桑椹期;8 h 20 min进入囊胚期;13 h 10 min进入原肠期;16 h 20min进入神经胚期;受精后18 h进入胚孔封闭期;21 h 30 min进入肌节出现期;27 h 20 min进入眼基出现期;28 h 40 min进入眼囊期;30 h 40 min进入尾芽期;32 h 30 min进入晶体出现期;34 h 40 min进入肌肉效应期;36 h 40 min进入耳石出现期;44 h进入心跳期;53 h 40 min进入眼色素形成期;60 h 40min进入血液循环期;68 h 30 min后开始出膜。杂交F1胚胎发育时序及形态特征均偏向母本花。     

土霉素处理对柑橘黄龙病的防治效果及PP2基因表达的影响

【目的】评价土霉素(oxytetracycline,OTC)药剂对不同发病程度柑橘黄龙病（Huanglongbing,HLB）的防治效果,并检测OTC处理后韧皮部关键基因——韧皮部蛋白2（PP2）的表达量变化,为HLB的有效防控提供科学依据,也为OTC作用机理研究提供参考。【方法】应用可有效抑制、杀死病原菌的OTC,树干定量注射0.1 g/树于不同发病程度HLB（初感染、轻度发病和重度发病3组）的4年生Valencia夏橙,注射后7、30、60、90 d定期采集Valencia叶片样品监测HLB致病菌Cadidatus Liberibacter asiaticus(Las)含量、淀粉含量及PP2基因表达量变化。树干注射OTC后90 d采集不同处理Valencia的嫩叶、成熟叶片及茎,进行淀粉染色光学显微观察（LM）,直观反映植株累积淀粉的变化。树干注射OTC后80 d调查柑橘嫩叶抽发的情况,综合一系列指标评价OTC对HLB的防治效果。【结果】注射OTC 0.1 g/树对初感染HLB的4年生Valencia植株治疗作用最明显,7 d后检测即为阴性,并可保持90 d,其成熟叶片的淀粉含量明显减少,但茎内仍有淀粉粒富集;轻度发病夏橙注射90 d后叶片内的Las含量从（1.68×10 ⁶±858884）cells/g叶片减至（7.21×10 ⁴±30981）cells/g叶片,下降幅度极为明显,其成熟叶片内的淀粉含量在90 d内一直呈下降趋势;重度发病植株注射后叶片内的Las含量从（4.10×10 ⁸±3.04×10 ⁸）cells/g叶片减至（2.80×10 ⁷±2.70×10 ⁷）cells/g叶片,但从数量而言仍然有较多分布,除了新长出的秋梢,其成熟叶及茎内的淀粉粒含量仍旧很大,说明0.1 g/株OTC不足以治愈4年生重度发病Valencia夏橙。对PP2基因表达分析结果显示,注射OTC后30 d,Valencia夏橙体内的PP2基因表达量大幅度下降,随后90 d内表达量稳定,与注射后30 d的表达量较为一致。 【结论】OTC可以用于HLB的防控,对初感染（Las含量为<9.00×10 ⁵cells/g叶片）及轻度发病（Las含量为9.00×10 ⁵—9.00×10 ⁷ cells/g叶片）的柑橘植株治疗作用较好,不适用于重度发病植株（Las含量为>9.00×10 ⁷ cells/g叶片）的治疗。注射OTC后,PP2基因表达量下降明显,说明OTC可有效减少韧皮部病菌等的胁迫压力。     

壬酸对华山松木蠹象成虫的拒食作用研究

壬酸对华山松木蠹象成虫有明显的拒食作用。在选择性拒食作用和完全拒食作用中,当浓度为4×10^4mg／L时的拒食效果在24和48h中都是最好的。选择性拒食作用中,24和48h的AFC。分别为3．24×10^2mg／L和5．68mg／L;完全拒食作用中,24和48h的AFC50分别为9．98×10^3和2．89×10^4mg／L。     

海黍子有性生殖相关形态建成因子分析

为了评估海黍子Sargassum muticum有性繁殖生殖力情况,利用统计学方法对海黍子有性生殖相关的形态建成因子进行了初步研究,通过分析藻体长度与侧枝数、侧枝长度与生殖托数、生殖托长度与生殖托挂卵数之间的数量相关性,利用回归方程估算了海黍子的个体生殖力。结果表明:海黍子成熟藻体平均长度为(164.5±59.9)cm,侧枝平均长度为(10.4±5.3)cm,生殖托平均长度为(9.3±1.5)mm,单个生殖托平均挂卵数量为(378±121)粒,各因子间存在线性正相关性(P0.05)。研究表明,单株海黍子成熟藻体能够产生(21~400)万粒受精卵,可基本满足1 m~2的采苗生产需要。     

Radio science results during the NEAR-shoemaker spacecraft rendezvous with eros

We determined the mass of asteroid 433 Eros, its lower order gravitational harmonics, and rotation state, using ground-based Doppler and range tracking of the Near Earth Asteroid Rendezvous (NEAR)-Shoemaker spacecraft and images of the asteroid's surface landmarks. The mass of Eros is (6.687 +/- 0.003) x 10(18) grams, which, coupled with our volume estimate, implies a bulk density of 2. 67 +/- 0.03 grams per cubic centimeter. The asteroid appears to have a uniform density distribution. The right ascension and declination of the rotation pole are 11.37 +/- 0.05 and 17.22 +/- 0.05 degrees, respectively, and at least over the short term, the rotation state of Eros is stable with no measurable free precession of the spin pole. Escape velocities on the surface vary from 3.1 to 17.2 meters per second. The dynamical environment of Eros suggests that it is covered with regolith and that one might expect material transport toward the deepest potential wells in the saddle and 5.5-kilometer crater regions.     

定点突变FGF21提高表达量研究

FGF21是一类具有重要糖脂代谢调节功能因子,是治疗2型糖尿病候选药物。但其在大肠杆菌中表达量低且主要以包涵体形式表达,为此根据FGF21与FGF家族同源序列差异,对FGF21进行定点突变以提高其表达量。以pSUMO-FGF21表达载体为模板,在突变位点两端设计引物,采用定点突变方法,将FGF21141位甘氨酸(G)突变为苯丙氨酸(F),构建突变FGF21表达载体pSUMO-mutFGF21;在大肠杆菌中进行表达,纯化mutFGF21蛋白。利用SDS-PAGE和Western blot鉴定分析突变蛋白,HepG2细胞糖吸收试验检测突变蛋白活性。结果成功对pSUMO-hFGF21进行突变,突变蛋白在大肠杆菌中成功表达,经SDS-PAGE分析,主要以可溶形式表达;与野生型FGF21(hFGF21)相比,表达量提高50%。Western blot表明mutFGF21可与FGF21抗体特异性反应。糖吸收试验显示mutFGF21具有与hFGF21一样生物活性并存在剂量依赖性,相比hFGF21,mutFGF21活性略有提高,说明定点突变FGF21(141位G突变为F)可显著提高FGF21表达量。     

Plasma diagnosis from thermal noise and limits on dust flux or mass in comet giacobini-zinner

Thermal noise spectroscopy was used to measure the density and temperature of the main (cold) electron plasma population during 2 hours (1.5x10(5) kilometers perpendicular to the tail axis) around the point of closest approach of the International Cometary Explorer (ICE) to Comet Giacobini-Zinner. The time resolution was 18 seconds (370 kilometers) in the plasma tail and 54 seconds (1100 kilometers) elsewhere. Near the tail axis, the maximum plasma density was 670 per cubic centimeter and the temperature slightly above 1 electron volt. Away from the axis, the plasma density dropped to 100 per cubic centimeter (temperature, 2x 10(4) K) over 2000 kilometers, then decreased to 10 (1.5x 10(5)K) over 15,000 kilometers; outside that region (plasma tail), the density fluctuated between 10 and 30 per cubic centimeter and the temperature between 1x 10(5) and 4 x10(5) K. The relative density of the hot population rarely exceeded a few percent. The tail was highly asymmetrical and showed much structure. On the other antenna, shot noise was recorded from the plasma particle impacts on the spacecraft body. No evidence was found of grain impacts on the antennas or spacecraft in the plasma tail. This yields an upper limit for the dust flux or particle mass, indicating either fluxes or masses in the tail smaller than implied by the models or an anomalous grain structure. This seems to support earlier suggestions that these grains are featherlike. Outside the tail, and particularly near 10(5) kilometers from its axis, impulsive noises indicating plasma turbulence were observed.