Tetraploid induction by inhibiting mitosis I in scallopChlamys farreri     

Yang Hui-ping  Guo Xi-ming  Chen Zai-zhong  Wang Yong-ping 《中国海洋湖沼学报》1999,17(4):350-358

Tetraploid induction was carried out by inhibiting mitosis I in fertilized eggs ofChlamys farreri. Mitosis I was blocked with cold shock (5–7°C), Cytochalasin B (0.75 mg/L) and 6-dimethylaminopurine (6-DMAP) (60–75 mg/L) when 60% fertilized eggs released polar body II at 20°C. At 4-cells embryo stage, the ploidy was determined by counting chromosome number. In control groups, most embryos were diploids (72.22%) and aneuploids (24.78%). In Cytochalasin B, cold shock and 6-DMAP treated groups, tetraploids were respectively 10.51%, 4.08%, and 13.34%; aneuploids were 43.10%, 35.93% and 29.16%, and triploids were 7.84%, 8.52% and 18.33%. At D-larva stage, ploidy was determined by flow cytometry (FCM). The ploidy analysis of day 2 larvae showed diploids in control group and also in three treated groups. Juvenile scallops (0.2–0.3cm) which were harvested in two control groups and two CB treated groups were all diploids through checking ploidy individually by FCM. Contribution No. 3648 from the Institute of Oceanology, Chinese Academy of Sciences. Contribution No. 238 from the Experimental Marine Biology Laboratory, Chinese Academy of Sciences. Project funded by grant (No. 819-01-07) from the Chinese Science and Technology Ministry and also by “Hundred Talents Plan” grant from the Chinese Academy of Sciences.  相似文献   

ANNUAL PRODUCTION OF FIVE SPECIES OF CHIRONOMIDAE (DIPTERA)IN HOUHU LAKE,A TYPICAL ALGAL LAKE(WUHAN,CHINA)   总被引：8，自引：2，他引：6  

阎云君  梁彦龄  王洪铸 《中国海洋湖沼学报》1999,17(2):112-118

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Optical spectroscopy of the radio pulsar PSR B0656+14     

S. Zharikov  R. E. Mennickent  Yu. Shibanov  V. Komarova 《Astrophysics and Space Science》2007,308(1-4):545-549

We have obtained the spectrum of a middle-aged PSR B0656+14 in the 4300–9000 Å range with the ESO/VLT/FORS2. Preliminary results show that at 4600–7000 Å the spectrum is almost featureless and flat with a spectral index α _ν ??0.2 that undergoes a change to a positive value at longer wavelengths. Combining with available multiwavelength data suggests two wide, red and blue, flux depressions whose frequency ratio is about 2 and which could be the 1st and 2nd harmonics of electron/positron cyclotron absorption formed at magnetic fields ～10⁸ G in upper magnetosphere of the pulsar.  相似文献   

基于双树复小波的CBERS-02B星遥感影像融合及评价     

于浩  孙卫东  常玲  甘甫平 《国土资源遥感》2009,20(1):55-59

以CBERS-02星全色、多光谱图像及IKONOS多光谱图像为数据源，利用离散小波变换和双树复小波变换进行融合试验。结果表明，双树复小波变换在空间细节表现力和光谱保持方面能够较好地达到平衡，较离散小波变换更能提高图像融合质量。通过融合方法对比分析可知，02B星全色波段不仅与其多光谱波段融合能够得到信息更加丰富的图像，而且与其它传感器数据融合同样有很好的目视效果和可读性，具有较大的应用前景。  相似文献   

'Notches' in the average profiles of bright pulsars     

Maura A. McLaughlin  Joanna M. Rankin 《Monthly notices of the Royal Astronomical Society》2004,351(3):808-812

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A model for 'double notches' in radio pulsar profiles     

G. A. E. Wright 《Monthly notices of the Royal Astronomical Society》2004,351(3):813-822

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XMM–Newton observations of GB B1428+4217: confirmation of intrinsic soft X-ray absorption     

M. A. Worsley  A. C. Fabian  A. Celotti  K. Iwasawa 《Monthly notices of the Royal Astronomical Society》2004,350(4):L67-L71

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Single pulses from PSR B1641–45     

Simon Johnston 《Monthly notices of the Royal Astronomical Society》2004,348(4):1229-1235

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Hubble Space Telescope imaging of the progenitor sites of six nearby core-collapse supernovae     

J. R. Maund  S. J. Smartt 《Monthly notices of the Royal Astronomical Society》2005,360(1):288-304

The search for the progenitors of six core-collapse supernovae (CCSNe) in archival Hubble Space Telescope ( HST ) WFPC2 pre-explosion imaging is presented. These SNe are 1999an, 1999br, 1999ev, 2000ds, 2000ew and 2001B. Post-explosion imaging of the SNe, with the HST ACS/WFC, has been utilized with the technique of differential astrometry to identify the progenitor locations on the pre-explosion imaging. SNe 1999br, 1999ev, 2000ew and 2001B are recovered in late-time imaging, and estimates of the progenitor locations on the pre-explosion imaging, with subpixel accuracy, have been made. Only the progenitor of the Type II-P SN 1999ev has been recovered, on pre-explosion F555W imaging, at a 4.8σ significance level. Assuming a red supergiant progenitor, the pre-explosion observation is consistent with   M _ZAMS= 15–18 M_⊙  . The progenitors of the other five SNe were below the 3σ detection threshold of the pre-explosion observations. The detection thresholds were translated to mass limits for the progenitors by comparison with stellar evolution models. Pre-explosion observations of the peculiarly faint SN 1999br limit the mass of a red supergiant progenitor to   M _ZAMS < 12 M_⊙  . Analysis has been extended, from previous studies, to include possible detections of high- T _eff, high-mass stars by conducting synthetic photometry of model Wolf–Rayet star spectra. The mass limits for the Type II-P SNe 1999an and 1999br are consistent with previously determined mass limits for this type of SN. The detection limits for the progenitors of the Type Ibc SNe (2000ds, 2000ew and 2001B) do not permit differentiation between high-mass Wolf–Rayet progenitors or low-mass progenitors in binaries.  相似文献   

Chandra observations of the X-ray jet in 3C 66B     

M.J. Hardcastle  M. Birkinshaw  D.M. Worrall 《Monthly notices of the Royal Astronomical Society》2001,326(4):1499-1507

Our Chandra observation of the FR I radio galaxy 3C 66B has resulted in the first detection of an X-ray counterpart to the previously known radio, infrared and optical jet. The X-ray jet is detected up to 7 arcsec from the core and has a steep X-ray spectrum, α ≈1.3±0.1 . The overall X-ray flux density and spectrum of the jet are consistent with a synchrotron origin for the X-ray emission. However, the inner knot in the jet has a higher ratio of X-ray to radio emission than the others. This suggests that either two distinct emission processes are present or differences in the acceleration mechanism are required; there may be a contribution to the emission from the inner knot from an inverse Compton process or it may be the site of an early strong shock in the jet. The peak of the brightest radio and X-ray knot is significantly closer to the nucleus in the X-ray than in the radio, which may suggest that the knots are privileged sites for high-energy particle acceleration. 3C 66B's jet is similar both in overall spectral shape and in structural detail to those in more nearby sources such as M87 and Centaurus A.  相似文献