紫贻贝(Mytilus edulis)养殖群体的遗传多样性及遗传结构分析

基于线粒体DNA的COⅢ基因序列对我国沿海重要经济贝类紫贻贝3个养殖群体(烟台、乳山、东极)的遗传多样性和遗传结构进行了研究。由PCR扩增获得32个体的COⅢ基因750bp的部分序列,其多态性遗传参数统计显示,32个个体共检出18个单倍型,总群体单倍型多样性指数(Hd)为0.946,核苷酸多样性指数(Pi)为0.0207,平均核苷酸差异数(K)为15.316,三个群体均显示出较丰富的遗传多样性。遗传分化系数(Fst)表明,东极群体与烟台群体及乳山群体已明显分化,而烟台群体和乳山群体间无遗传分化,并且存在着较大的基因流。     

Multiwavelength Study of two Unidentified γ-ray Sources

Most counterparts of the identified low-latitude γ-ray sources are isolated neutron stars (INSs). Since INSs are characterized by an extremely high value of f _X/f _opt, a systematic X-ray/optical coverage of the fields of unidentified low-latitude γ-ray sources is the best way to unveil INS counterparts of unidentified sources. Since the low-latitude sources are heavily affected by the interstellar absorption in both the X-ray and optical bands, we decided to apply the above strategy to two middle-latitude EGRET sources, which could belong to a local galactic population: 3EG J0616-3310 and 3EG J1249-8330. Here we report on the global X-ray characterization of about 300 objects, on their candidate optical counterparts and on the preliminary results of their identification.     

Maps of Titan's surface from 1 to 2.5 μm

We have acquired resolved images of Titan with the adaptive optics systems PUEO/KIR at the CFHT (Hawaii) and NAOS/CONICA at the VLT (Chile). We report here on images and maps (when data at several orbital phases are available) of Titan's surface from observations taken during the last 4 years (2001-2004) in all the methane windows between 1 and 2.5 μm (namely, at 1.08, 1.28, 1.6, and 2 μm). We present the only complete maps of Titan currently available at 1.3 μm, a spectral window where Titan appears particularly bright in spectroscopy, with a resolution of about 200 km at best on the ground. Our surface maps show the bright and dark regions sharing Titan's landscape with as much detail as possible from the ground and with high contrast in most cases. From the information gathered by comparing the maps at different wavelengths we derive constraints on the ground's composition. Our results could complete/optimize the return of the Cassini-Huygens mission.     

Broadband submillimeter measurements of the full Moon center brightness temperature and application to a lunar eclipse

We report on observations of the full Moon brightness temperature covering the frequency range of 300-950 GHz, and also on observations of the lunar eclipse of July 16, 2000, though only covering the frequency range of 165-365 GHz due to poor atmospheric transmission at higher frequencies. All observations were performed from the summit of Mauna Kea (HI) using a Fourier Transform Spectrometer mounted on the Caltech Submillimeter Observatory and supplemented by measurements of the atmospheric opacity using a 183 GHz Water Vapor Monitor. The telescope was pointed to the center of the lunar disk (with a footprint of ∼45-15 km on the Moon at 300 through 900 GHz). In order to obtain the correct values of the Moon brightness temperatures at all frequencies we carefully corrected for the atmospheric absorption, which varies across the submillimeter domain. This correction is fully described. The measured pre-eclipse brightness temperature is around 337 K in the 165-365 GHz range. This temperature slightly increases with frequency to reach ∼353 K at 950 GHz, according to previous broader band data. The magnitude of the temperature drop observed during the eclipse at 265 GHz (central frequency of the band covered) was about ∼70 K, in very good agreement with previous millimeter-wave measurements of other lunar eclipses. We detected, in addition, a clear frequency trend in the temperature drop that has been compared to a thermal and microwave emission model of the lunar regolith, with the result of a good match of the relative flux drop at different frequencies between model and measurements.     

Constraining the surface properties of Saturn's icy moons, using Cassini/CIRS emissivity spectra

We have conducted a search for emissivity features in the thermal infrared spectrum of the icy satellites of Saturn, Phoebe, Iapetus, Enceladus, Tethys, and Hyperion, observed by the Composite Infrared Spectrometer (CIRS) on board the Cassini spacecraft. Despite the heterogeneity of the composition of these bodies depicted by Earth-based and Cassini/VIMS observations, the CIRS spectra of all satellites are undistinguishable from black-body spectra, with no detectable emissivity feature. However, several materials, which have been detected on the surface of the same bodies, present emissivity features in the analyzed spectral range. In particular, water ice presents features with sufficient contrast to be detected by CIRS. Here we study the physical causes of the absence of features by simulating the effects of intimate mixtures using models of directional emissivity for optically thick surfaces for different particle sizes and abundances, and porosities. The simulations include a set of materials detected on the Phoebe's surface, like water ice, hydrated silicates, and organics. We find that featureless spectra can be produced in three scenarios: (1) ice particles with large sizes, (2) mixtures of ices dominated by dark contaminants, and (3) small particles with large porosity. Constraints imposed by the NIR spectra of the satellites favors the latter scenario as the more likely explanation to the absence of emissivity features on the icy satellites of Saturn.     

CLASS B2108+213: a new wide-separation gravitational lens system

We present observations of CLASS B2108+213, the widest separation gravitational lens system discovered by the Cosmic Lens All-Sky Survey. Radio imaging using the VLA at 8.46 GHz and MERLIN at 5 GHz shows two compact components separated by 4.56 arcsec with a faint third component in between which we believe is emission from a lensing galaxy. 5-GHz VLBA observations reveal milliarcsecond-scale structure in the two lensed images that is consistent with gravitational lensing. Optical emission from the two lensed images and two lensing galaxies within the Einstein radius is detected in Hubble Space Telescope imaging. Furthermore, an optical gravitational arc, associated with the strongest lensed component, has been detected. Surrounding the system is a number of faint galaxies which may help explain the wide image separation. A plausible mass distribution model for CLASS B2108+213 is also presented.     

Are Type Ia Supernovae Reliable Distance Indicators？

Recent applications of type Ia supernovae(SNe Ia)in cosmology have successfully revealed the accelerating expansion of the universe.However,as distance indicators used in measuring the expansion history of the universe and probing the nature of dark energy,these objects must pass more strict tests.We propose a K-S test to investigate if there exists any systematic bias when deriving the luminosity distances under the standard candle assumption. Two samples,one comprising 71 high-redshift SNe Ia and the other,44 nearby ones,are used in our investigation.We find that it is likely there exists a bias in the adopted samples,which is probably caused by a systematic error,e.g.in the color parameter used in the luminosity calibration and a bias may be caused by the SN evolution or by varying properties of the dust surrounding the SNe Ia.     

Dehydration reaction and isotope front transport induced by CO2 infiltration at Nuliyam, South India

The field relations from a quarry at Nuliyam, South India, illustrate dehydration of an amphibolite facies gneiss to granulite facies charnockite by CO₂ influx, over a scale of 30 m. Both the calc-silicate source of the fluids and the full extent of their penetration into the gneiss are preserved in a continuous section. Fluid flow is by a hydraulic fracture mechanism, but is thought to be pervasive. The sharp reaction front predicted by the continuum mechanical theory for advective fluid transport is not observed. The front spreading is on too large a scale for either diffusive or dispersive control and is due to local kinetic disequilibrium between the fluid and rock, although the divariant nature of the reaction may also have a limited effect. The time-integrated fluid flux varies from the instantaneous porosity at the fluid front to 20 vol. % adjacent to the calc-silicate. Carbon isotope budgets suggest that decarbonation of the calc-silicate by a Rayleigh fractionation process provides a sufficient source for the CO₂ influxing into the gneiss. Graphite abundances vary from 0.01 to 0.1% (by weight), it is principally derived by precipitation from the fluid and may be modelled from phase equilibria. Carbon isotope fronts coincide with the reaction front on the scale of sampling, although isotopic disequilibrium between graphite and inclusion-CO₂ also implies local fluid-rock disequilibrium.     

大气CO_2浓度升高对海洋浮游植物影响的研究进展

工业的迅速发展、化石燃料的燃烧、森林的大量砍伐等引起大气中温室气体,特别是CO2的浓度逐年上升,据预测,到本世纪中叶大气CO2浓度将达到目前的2倍,即达到700μL L-1[1]。由CO2等微量气体浓度增加所造成的“温室效应”已成为影响全球变化的一个重要而又不可忽视的因素。近几年来通过“全球海洋通量的联合研究”表明,海洋对大气中CO2的净吸收主要是通过一系列被称为“生物泵”的生物学过程来实现,其中海洋浮游植物通过光合作用把海水中溶解态CO2转化为颗粒态是“生物泵”中一个重要的生物化学过程[2],可见海洋浮游植物对海洋回收大气C…