An advanced irradiation facilities and its usage     

康兴伦  陈洪涛  江雪艳  宁劲松  于志刚  朱校斌  张卫国 《中国海洋湖沼学报》2006,24(2):212-214

1 INTRODUCTION Carrier type gamma irradiation, a new tech- nology have been developed rapidly in recent dec- ades in industry, agriculture, and science and tech- nology. In Qingdao Irradiation Center (QIC), a car- rier-type irradiator in overlapping sourc…  相似文献   

Chemical evolution of circumstellar matter around young stellar objects     

Ewine F. Van Dishoeck  Geoffrey A. Blake 《Astrophysics and Space Science》1995,224(1-2):237-249

Recent observational studies of the chemical composition of circumstellar matter around both high- and low-mass young stellar objects are reviewed. The molecular abundances are found to be a strong function of evolutionary state, but not of system mass or luminosity. The data are discussed with reference to recent theoretical models.  相似文献   

岱衢洋大黄鱼(Pseudosciaena crocea)胚胎与仔稚幼鱼发育   总被引：1，自引：0，他引：1       下载免费PDF全文

程顺  杜晨  竺俊全  吴雄飞 《海洋科学进展》2014,32(4)

对养殖岱衢洋大黄鱼进行人工催产、自然产卵获得受精卵,在人工培育条件下观察了其胚胎及仔稚幼鱼发育过程。结果表明:1)岱衢洋大黄鱼受精卵呈圆球形,浮性;2)在水温23.0~24.0℃、盐度22.1条件下胚胎发育历时25.5h,主要经历了卵裂期、囊胚期、原肠胚期、神经胚期、器官形成期及孵化期等阶段;3)在水温22.0~24.0℃、盐度22.1~23.4条件下,仔鱼发育经历了前期仔鱼(0~7日龄)和后期仔鱼(8~18日龄);4)19日龄进入稚鱼前期,各鳍齐全;5)29日龄进入稚鱼后期,鳞片出现;6)36日龄以后全身被鳞,进入幼鱼期。仔稚幼鱼生长方程为TL=0.570 3 D+0.750 1(R2=0.965 8),全长和日龄呈极显著线性相关。  相似文献   

Learning about distant places through the Internet: Young students as global citizens?     

Ståle Angen Rye 《Norsk geografisk tidsskrift. Norwegian journal of geography》2013,67(3):148-156

The article explores how the use of the Internet in school settings influences the way young people develop as citizens in an interconnected world and the possible implications for teaching geography subject at school. First, this topic is approached theoretically through a discussion of new forms of citizenship. The issue is investigated by using interview data and observations on the use of the Internet by upper secondary school students in Norway when searching for information about distant places. During the interviews, knowledge about tropical rainforests was used as a practical example. The main finding is that although the students could access information about a large part of the world from their laptop, a distance remained between the students and the rainforests and those who live in them. The article also reveals that, although it is often argued that the national context is weakened as a frame for civic engagement, the students referred to it as a basic frame when engaging with what is distant. Thus, it may be questioned how the use of the Internet in schools contributes to the development of students as global citizens.  相似文献   

斜带石斑鱼人工育苗技术试验   总被引：19，自引：2，他引：19  

周仁杰  林涛 《台湾海峡》2002,21(1):57-62

试验获得初步成功：用50万粒受精卵孵得34.8万尾仔鱼，经60日龄培育，获全长20.5-48.5mm（平均全长26.5mm)的斜带石斑鱼鱼苗0.4万尾，育苗成活率达1.2%。试验期间育苗池水温、盐度的变化范围分别为27.3-30.5℃和31.5-32.0。试验采用如下铒料系列：牡蛎担轮幼虫-轮虫-卤虫无节幼体-卤虫无节幼体 冰冻桡足类、海水技角类。试验经历了3个死亡高峰期，它们分别出现在育苗初期仔鱼开口阶段、稚鱼期30-38日龄阶段和进入幼鱼期以后，本文讨论分析了其成因。  相似文献   

Pathways and Processes: Reviewing the Role of Young Adults in Urban Structure     

Nick Revington 《The Professional geographer》2018,70(1):1-10

Challenges arising from changing demographics, expensive housing, and precarious labor have prompted recent interest in the residential geographies of young adults. Yet, despite attention to young adults' diverse housing pathways, I argue that greater focus is needed on the place-based and spatial underpinnings and effects of particular housing pathways: Connections to urban processes of “youthification”—the concentration of young adults in dense neighborhoods—and “studentification”—whereby an area becomes dominated by university students—remain underdeveloped, as do linkages between these phenomena and gentrification. I explore these connections through a critical review of extant literature to show that the enactment of some pathways is associated with particular urban processes, which might foreclose certain pathways for other individuals. Finally, I identify three crucial areas of inquiry: (1) how youthification, studentification, and gentrification interact; (2) how these processes shape and are shaped by diverging individual housing pathways; and (3) how differences among young adults such as race, ethnicity, and gender intersect with age in the course of these processes.  相似文献   

人文与经济地理学的传承与创新：青年学者的行动     

陈明星  陆大道  唐常春  刘承良  叶玉瑶  丁建军  王姣娥  刘晔  唐志鹏  孙中伟  陈东  李钢  孙伟  李鹤  潘峰华  张圆刚  李玉恒  李裕瑞  魏冶  赵建吉  彭立  高菠阳  胡志丁  钱丽芸  姜炎鹏  董冠鹏  杨传开  虞虎  安宁  戚伟 《地理研究》2018,37(10):2096-2124

2018年是中国改革开放40周年,也是“科学的春天”40周年。随着中国进入特色社会主义新时代,人文与经济地理学也将迈入新时代。青年学者恰好处在承前启后的这一时期,围绕学科传承和创新发展需要,面向新时代国家和经济社会发展的现实需求,青年学者积极行动起来,努力学习和传承人文与经济地理学前辈所建立的学科体系,并力图继续开拓和创新。一是助力建设学科文化,打造具有学科认同感和归属感的学术共同体。二是在向西方学习的同时,加强中国特色的自主理论建构与创新。三是向相关学科方向学习,加强交叉与综合的数据和方法创新,建设科学化、多元化的研究方法体系。四是青年学者更需要踏实认真的态度,找准个人研究领域方向,求真务实并力图创造新的知识,不断提升研究深度。人文与经济地理学的学科梦必将在一代代青年学者的接力奋斗中变为现实。  相似文献   

Education in cartography: what is the status of young people’s map-reading skills?     

Kristien Ooms  Philippe De Maeyer  Lien Dupont  Nina Van Der Veken  Nico Van de Weghe  Stephanie Verplaetse 《制图学和地理信息科学》2016,43(2):134-153

Due to recent technological progress, maps have become more popular than ever before. This is especially true for young people, who interact with these technologies on a daily basis. Therefore, it is essential that these potential map users possess sufficient knowledge and skills to process the content of cartographic products. A user study was conducted during which pupils (aged 11–18 years) and geography students (>18 years) had to solve a number of cartography questions using topographic maps. The data were analyzed statistically, taking into account a number of potentially influencing factors (user characteristics) on the participants’ results: age, gender, youth club membership, knowledge about the area, among others. The results show a rising trend in the pupils’ scores with increasing age, which can be explained by education in cartography at school. Geography students perform much better, but no influence of any other user characteristics was detected. For pupils, knowledge about the area and gender might be considered as influencing factors. However, the detected influence of gender depends on the scoring system.  相似文献   

粤北长塘盆地晚白垩世早期流纹岩的成因:地球化学和Sr-Nd-Pb-Hf-O同位素制约     

劳玉军  巫建华  徐勋胜 《岩矿测试》2016,35(5):558-567

长塘流纹岩为"大量流纹岩-少量玄武岩"构成的不对称双峰式火山岩组合的酸性端元,前人对年代学研究认为是目前华南识别的燕山期最年轻的流纹岩(SHRIMP年龄96.8 Ma),但在岩石地球化学特征及成因方面尚未深入研究。本文通过全岩主微量元素、Sr-Nd-Pb-O和锆石Hf同位素研究得到:流纹岩为亚碱性弱过铝质岩石,稀土元素富集,轻重稀土分馏明显,Eu负异常;具有较小的(~(87)Sr/~(86)Sr)_i、较高的εNd(t)和较低的(~(206)Pb/~(204)Pb)_i、(~(207)Pb/~(204)Pb)_i、(~(208)Pb/~(204)Pb)_i值;锆石的εHf(t)值较高且Hf模式年龄和全岩基本一致,均显示为新生下地壳岩浆;全岩的δ18O值较高。结合区域地质资料,本文认为长塘流纹岩是在晚白垩世早期拉张环境下,源于EMⅡ富集地幔的岩浆混染少量下地壳物质形成新元古代新生下地壳,发生熔融产生的岩浆在上升过程中经历结晶分异演化后喷出地表的产物。晚白垩世早期流纹岩成因对华南陆壳拉张减薄到正常厚度时间节点提供了证据。  相似文献   

Youth transitions and going to university: the perceptions of students attending a geography summer school access programme     

Peter E Hopkins 《Area》2006,38(3):240-247

This paper contributes to understandings of youth transitions in childhood and youth geographies through the use of a participatory diagramming exercise with students studying geography in a summer school access programme at a Scottish university. In particular, the paper explores young people's perceptions about adult/child binaries and their hopes and fears in applying to university. The discussion highlights the extended nature of youth transitions: the usefulness of participatory diagramming as a research method and teaching technique for this group; and the consequences that the increasing interest in childhood and youth geographies might have on teaching and learning in human geography.  相似文献