星系中心大质量黑洞及潮汐瓦解恒星事件

黑洞潮汐瓦解恒星事件(Tidal Disruption Events,TDE)是星系中心黑洞瓦解进入其潮汐瓦解半径内的恒星并吸积恒星碎片物质而产生的一种剧烈辐射耀发现象.TDE的能谱和光变特征中蕴含了中心黑洞和被瓦解的恒星的信息,为我们证实和普查宁静星系中的黑洞,研究其参数、吸积过程和喷流产生、以及核区星际介质等提供了可能.TDE还可能提供中等质量黑洞和双黑洞存在的证据.TDE的观测和理论已成为一个新开辟的天体物理研究领域,但目前的进展受制于探测到事件太少(尤其是在X射线波段),且观测数据普遍质量不高.TDE的发生率很低,要探测大样本的事例需要监测足够大的空间体积.爱因斯坦探针卫星(Einstein Probe,EP)覆盖了0.5–4 keV的软X射线波段(接近TDE耀发时的辐射峰值能段),具有大视场以及高灵敏度,非常利于对TDE的探测.预期爱因斯坦探针卫星每年可以发现约几十至上百例TDE,其中有约10例或更多具有相对论性喷流特征.这将使我们可以获得较为完备、具有统计意义的TDE的样本,为进一步研究黑洞的存在和统计性质、增长和演化、发现中等质量黑洞和大质量双黑洞等提供了新的途径.中国科学院空间科学战略性先导科技专项(编号:XDA15052100);;北京大学“985工程”建设项目“星团环境对双黑洞形成演化过程的干扰及其对引力波探测的影响”资

RAPD ANALYSIS of SEEDLING GENOMIC DNA VARIATIONINDUCED BY N--+ IONS IMPLANTATION IN STEVIA SEEDS

应用rAPd 技术检测经低能氮离子注入甜菊纯系种子引起的幼苗基因组dnA 变异。筛选出OPJ系列中的15 种引物对实验及对照基因组dnA 进行了PCr 扩增，共获扩增片段103 条，分子量在0.3 - 3kb 之间，其中5 种引物OPJ- 1 ，7 ，9，11 ，12 扩增出差异片段12 条。结果表明，低能氮离子注入甜菊种子可引起体内基因组dnA 发生突变；rAPd 技术是检测基因组dnA 发生诱变的一种简便、有效方法。本文同时探讨了离子强度和TAg dnA 聚合酶用量对甜菊rAPd 分析结果的影响，以及氮离子注入诱变效应的可能机制。The paper reports the genomic DNA variation induced by N+ ion implantation in Stevia seeds using RAPD analysis.The total of 103 bands has been amplified from Stevia genomic DNA with fifteen screened primers.The molecular weight of every amplified fragment is between 0.3kb and 3kb.There are twelve polymorphic bands have been amplified by four 10bp primers (OPJ-1, 7,9,11,12).The result show that implantation of N+ ion beam can induce genomic DNA variation.RAPD analysis is a simple and efficient method in detecting genomic DNA variation.The effect of different ion intensity and the quantity of Tag DNA polymerase on the result of RAPD analysis as well as the possible mechanism of biological effects induced by N+ ions implantation is also discussed.国家自然科学基金!重大项目（19890300号

Effects of Low-energy Carbon Ion Implantation on the Growth and Development of Chloroplast of Stevia rebaudiana

研究了能量为１００ ｋｅＶ，剂量为１０１５／ｃｍ ２ 的碳离子对甜菊种子萌发率、幼苗生长发育及叶绿体结构的影响．证明被注入种子出现萌发迟缓、生长速度减慢、植株株型变矮和生物量减少等生物学性状变化；幼叶细胞的叶绿体发育分化减慢、基质类囊体形成滞后、基粒数及基粒类囊体片层减少；部分幼叶细胞叶绿体膜破损、基质片层断裂直至叶绿体解体（约占二十分之一）．表明该能量剂量的碳离子注入将影响种子的生长发育，其原因之一是叶绿体发育迟缓和叶绿体的损伤．该研究为低能碳离子对甜菊诱变育种提供参考依据．This paper reports the effects of carbon ion implantation at 100 keV and 10 15 /cm 2 on the seed germination rate, development, growth, and chloroplast structure of Stevia rebaudiana seedling. The result showed the following changes of the biological characters of the ion implanted seeds in:(1) the retardation of the seed germination, the deceleration of the growth speed, the stunt of plant height, and the decrease of biomass;(2)the deceleration of differentiation and growth of the chloroplast in young leaf cells, the retardation in forming thylakoid, the decrease of the grana numbers and thylakoid lamella; and (3) the damage of the chloroplast membrane, the cleavage of stroma lamella and/or the decomposition of chloroplast(ca.5%).The experimental result proved that the carbon ion implantation at the above energy and dose surely influenced the development and growth of S. rebaudiana seed because of the lesion and development retardation of chloroplast. The study suggested a reference to the induced breeding of S. rebaudiana by low energy carbon ion implantation.国家重大项目资助!课题（19890300