Disk wind in young binaries with low-mass secondary components: Optical observational manifestations

We consider a model of a young binary with a low-mass secondary component. Mass accretion from the remnants of the protostellar cloud onto the binary components is assumed to take place in accordance with current models; i.e., it proceeds mainly onto the low-mass component. The accretion is accompanied by mass outflow (disk wind), whose low-velocity component can be partially captured by the primary component. As a result, an asymmetric common envelope is formed. Its densest part is involved in the orbital motion of the secondary and can periodically shield the primary component of the binary from the observer. Assuming a standard dust-to-gas ratio for the disk wind (1: 100), we calculated the possible photometric effects from such eclipses and showed that they could be observed even at moderate accretion rates onto the low-mass binary component, ∼10⁻⁸–10⁻⁹ M _⊙ per year. In this case, the parameters of the minima depend on the model of the disk wind, on the ratio of its characteristic velocity to the orbital velocity of the secondary, and on its orbital inclination to the line of sight. These results can form the basis for interpreting a wide range of phenomena observed in young stars, such as the activity cycles in UX Ori stars, the unusually broad minima in some young eclipsing systems, etc., and for searching for substellar objects and massive protoplanets. In addition, the peripheral parts of the gas and dust disk around a young binary can fall within the shadow zone produced by the opaque part of the common envelope. In such cases, a shadow from the common envelope must be observed on the disk; this shadow must move over the disk following the orbital motion of the low-mass component. Detection and investigation of such structures in the images of protoplanetary disks may become a method of searching for protoplanets and studying binaries at early stages of their evolution.     

An advanced irradiation facilities and its usage

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…     

Chemical evolution of circumstellar matter around young stellar objects

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.     

夏、冬两季真鲷仔、稚、幼鱼消化酶活性的比较

通过夏、冬两季真鲷仔、稚、幼鱼蛋白酶、淀粉酶和脂肪酶活性的变化研究表明,夏、冬两季3种消化酶变化趋势基本相似。蛋白酶的活性冬季比夏季低1个数量级;淀粉酶的活性冬季比夏季低1倍左右;脂肪酶的活性冬季高于夏季,且一直维持在相对稳定的水平。结果表明,3种酶活性受温度影响外,冬季脂肪酶的高活性对鱼苗的生长、成活具有重要意义。     

Social geography of risk: The role of time,place and antiretroviral therapy in conceptions about the sexual risk of HIV in Kahe,Kilimanjaro, Tanzania

The epidemiological pattern of HIV/AIDS in Africa and Tanzania is characterized by geographical variations in HIV prevalence. Despite the geographical variations, heterosexual contact remains the predominant mode of HIV transmission. The article examines the interrelationships of social, spatial and temporal issues in explaining the sexual risk of HIV/AIDS amongst youths in rural Tanzania. Drawing on discussions with young people, the authors employ a comparative approach to establish categories of social practices that explain HIV risk. HIV risk is largely influenced by social interaction as youths engage in routine day-to-day activities in different geographical locales. The availability of antiretroviral treatment ushered in new dynamics in locally available strategies to manage the risk of HIV infection. Gender relations appear to have an underlining influence in determining the timing and place of risk as well as ways of controlling risk. The study participants emphasized both social and biomedical interventions to manage and control sexual activity and risk. Youth-focused and community-wide interventions addressing HIV prevention, care and treatment need to recognize the fact that the HIV epidemic in Tanzania is increasingly becoming a rural phenomenon structured by a wide range of local, national and global processes.     

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

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.     

应用卫星多角度遥感识别被老鼠和昆虫破坏的草地(英文)

该文研究用ＡＶＨＲＲ数据监测Ｒｕｏｒｇａｉ县大草原被老鼠、昆虫破坏的情况。鼠虫危害区的光谱特征是：ＡＶＨＲＲ数据的可见光波段（０．５８－０．６８μｍ）地面反射率（ＣＨ１）较高，近红外波段（０．７２５－１．１μｍ）的地面反射率（ＣＨ２）较低，红外辐射波段（３．５５－３．９３μｍ）的亮度温度（ＣＨ３）较高；鼠虫危害区的遥感信息特征在雨季７月最为明显；可用比值植被指数ＲＶＩ（ＣＨ２／ＣＨ１）确定鼠虫危害程度；用多角度获得的ＲＶＩ可反映鼠虫危害。结果显示在这方面上，多角度遥感比多波段光谱法能更好地识别老鼠、昆虫破坏的地区。     

人文与经济地理学的传承与创新：青年学者的行动

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。     

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

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.     

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

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.