彩叶草叶片cDNA文库的构建与分析

用植物(叶)总RNA抽提试剂盒提取彩叶草红色品种顶部叶片总RNA,用SMART cDNA Library Construction Kit构建cDNA文库。经测定原始文库滴度为1.2×106 pfu/ml,扩增总文库滴度为6.7×109 pfu/ml,重组率达到98%,插入片段在0.5 kb到2 kb之间,1 kb以上的占60%。通过PCR检测,从总文库中检测到了彩叶草CHS、DFR 及ANS基因的特异片段。各项指标都表明,已获得较高质量的cDNA文库,为彩叶草叶色基因的分离克隆,彩叶草类黄酮类色素合成的分子调控的研究奠定了基础。     

中国养殖业中的外来物种入侵现象调查分析

采用文献调研、实地考察与专家咨询相结合的方法对调查了中国养殖业中外来物种入侵现象进行了调查。初步查明了中国养殖业中外来入侵物种种类共计27科40种,其中外来入侵水生植物、陆生植物、无脊椎动物、脊椎动物分别为5种、10种、3种、22种;来源于美洲、欧洲、非洲、亚洲和中国不同生态环境的分别有22种、3种、6种、3种、6种;中国养殖业中的外来物种入侵途径以不当的有目的的引入为主;外来物种入侵已对中国生物多样性、人民健康和经济造成了严重影响。针对中国养殖业中造成外来物种入侵的原因,需要采取必要的防治措施以促进中国养殖业的顺利发展。     

气候变化背景下应重视生物入侵问题

<正>开着飞机杀虫子?看似荒唐却是事实。北京市就曾经出动飞机450架次来灭杀美国白蛾。为了剿灭白蛾,北京除增设测报点严密监测外,还筹集了3000万元专项资金用于防控。而这些都是外来生物入侵惹的祸。外来生物入侵指的是非本地的生物(包括植物、动物和微生物)通过各种方式进入一个特定的生态系统,并对该生态系统、栖境、物种、人类健康带来威胁的现象。外来入侵生物的生物学特征包括:首先,生态适应能力强。也就是说对生存条件要求的不严格、不苛刻。第二,繁殖能力强。它产生的花粉量大,产生的种子或果实多,保证它传播     

中国面临外来生物入侵挑战与防控对策研究——以草地贪夜蛾为例

外来生物入侵是一个影响深远的全球性问题,对各国的生态系统、环境、健康、社会、经济发展具有重大的影响。尤其是近年来,随着全球气候变暖和全球贸易自由化的加快,外来入侵生物的种类和数量呈现快速增长趋势,生物入侵的威胁日益加重,若无行之有效的防控措施,外来生物入侵可能会形成“生物恐怖”。本研究以2019年1月联合国粮农组织全球预警的重大害虫——草地贪夜蛾第一次大范围入侵中国为例,分析了入侵生物对中国经济、生态与社会的影响,阐述了外来生物可能的入侵途径,剖析了当今时代背景下中国外来生物入侵防控面临的挑战,并针对入侵生物的入侵特点和影响,提出了完善“统一监管、分工负责”的管理机制、加快外来入侵物种立法、管理体系健全、执法监督体系建立、加强外来入侵物种的基础研究和防控网络建设、深入推进科普宣传与教育等综合防控对策。     

加强对外来入侵物种的管理力度

2012年入夏,水花生、水葫芦、刺萼龙葵等外来入侵水生生物在我国一些地区疯长,呈暴发态势,严重威胁了当地农牧渔业生产和航运交通安全。为了防范外来生物入侵突发灾害,农业部科教司和中国农学会在湖北省咸宁市和吉林省白城市举办2012年全国外来入侵生物灭除活动,国内有关专家在     

植物入侵的危害及防治

植物入侵是指某种植物从外地自然传入或人为引种后成为野生状态,在当地适宜的土壤、气候和缺少天敌抑制的条件下得以迅速繁殖,并取代原有植物,破坏当地生态或经济。外来入侵植物一般多为一、二年生草本植物,具有生活周期短,种子数量巨大,繁殖和传播方式多样,灵活适应环境变化等特征。大部分外来物种成功入侵后,其长势难以控制,压制或排挤本地物种,形成单优势种群,危及本地物种的生态,最终导致生物多样性的丧失。     

水葫芦和紫茎泽兰的启示——话说外来植物入侵

<正> 1998年出版的《中国生物多样性国情研究报告》指出:"目前中国已知的外来有害植物近60种。"报告还列出了58种"中国已知外来有害植物",其中包括水葫芦、紫茎泽兰、飞机草、普通豚草等一些被媒体屡次报道的外来入侵植物。前不久,笔者在贵州、广东等地又目睹了紫茎泽兰、薇甘菊(一种新出现的外来入侵者)等外来植物的猖撅入侵,对外来有害生物对本地生态系统和生物多样性的威胁产生了深刻认识。但静下心来细细想想,又有一些异样的感觉。是敌人,还是朋友在我们的周围,植物"入侵者"的身影时常可见。据专家统计,世界各地的杂     

中科院研究表明:百年来全球变暖导致入侵物种定居速度加快

<正>近百年来,外来入侵昆虫在全球范围内的定居速度逐步加快。这种趋势虽然与日益增长的国际贸易导致的物种引入密切相关,但与环境变化的相关性被关注不够。为了更好地了解和控制生物入侵,阐明全球变暖与入侵物种定居速度变化的关系就非常重要,尤其是昆虫等变温入侵动物。     

生物入侵危害的指标体系探讨

生物入侵已经对中国的生物多样性、生态环境和国民经济产生严重的威胁。生态安全指标体系的构建：生物入侵危害研究的深入;以及众多其他领域指标体系研究框架的成果为生物入侵危害指标体系的构建提供了依据。在总结了近年来关于生物入侵造成危害相关研究的基础上,根据频度分析法。将众多文献中的危害指标进行筛选、整理,并根据客观形势的发展和需要提出一些新的指标。结合指标体系研究中一些比较成熟的框架,尝试构建了生物入侵指标体系。旨在为政府部门及科研机构更科学的评价生物入侵危害提供一个可行的框架。     

中科院发现外来入侵植物——椴叶鼠尾草

<正>日前,中国科学院昆明植物研究所研究人员在对鼠尾草属进行研究的过程中,确认了一种近年来在昆明附近有迅速蔓延趋势的外来鼠尾草——椴叶鼠尾草。据介绍,椴叶鼠尾草是一种原产中美洲的杂草,已入侵到墨西哥、美国、埃塞俄比亚、南非和澳大利亚等地。研究     

The response of U.S. regional demographics to import shocks

We analyze regional demographic responses to increased competition from Chinese imports. Treating the opening up of the Chinese economy in recent decades as an exogenous shock to the degree of trade exposure faced by U.S. regions, we find that demographic characteristics such as education level, population growth, immigrant share, and age structure, are not significantly impacted by increased Chinese trade exposure. We also discuss possible mechanisms that may explain this finding and explain why our results may differ in direction from previous studies. Specifically, our finding is consistent with a story where moving costs hamper labor mobility and significant demographic shifts do not occur even after employment falls due to trade exposure.     

The U.S.-Canada Free Trade Agreement and Commodity Transportation Services among U.S. States

The Free Trade Agreement (FTA) implemented beginning in 1989 by the United States aid Canada will have significant impacts on bilateral trading patterns. In addition to its long-term, investment-related repercussions, the FTA will affect the volume, commodity composition, and spatial distribution of trade and, consequently, the transportation services required to move commodities between the two nations. This paper examines the changing spatial structure of U.S.-Canadian trade under the FTA. It employs commodity-specific analyses of tariffs and non-tariff barriers, as well as price and income elasticities of demand, to estimate sectoral and special changes among U.S. states in total, land, water, and airborne commodity flows since 1988 attributable to the FTA. The analysis details the assumptions and methodology used, elaborates upon the likely consequences for me nation's ten largest customs districts, particularly New York, and concludes with some comments on other forces that may alter the expected results.     

美国蜂业支持政策及其对中国的启示

养蜂业由于蜜蜂为作物授粉而对农业生产起着关键作用,然而当前中国的蜂产业政策还十分欠缺,政府没有为养蜂业发展提供优良的政策环境。因此为了提出完善中国蜂业支持政策体系的政策建议,促进中国蜂业较快发展,本研究使用归纳分析的方法,分析和借鉴了美国相对健全的蜂业支持政策体系。分析结果表明：美国的蜂业支持政策可分为以下几类——以稳定养蜂者收入为目标的蜂蜜价格支持政策;以保护国内蜂蜜生产者利益为目标的蜂蜜贸易保护政策;以减轻养蜂灾害损失为目标的蜂业保险和紧急援助政策;以解决蜂业病虫害和蜂群消失问题为目标的科研支持政策以及以监管养蜂生产环节为目标的养蜂注册与检疫政策。结合中国蜂业政策现状,中国蜂业支持政策体系要从开发政策性蜂业保险并辅以养蜂风险救助,加大财政对蜂业补贴力度,加强对蜂业科研的支持,加强养蜂生产环节控制几个方面来完善。     

The Changing Regional Structure of the U.S. Economy

This paper utilizes newly available industry-specific historical measures of Gross Regional Product to highlight the changing regional structure of the U.S. economy between 1963 and 1986. During this period, the percentage of U.S. output produced in the eight different regions changed significantly. The largest changes occurred in the Great Lakes (?3.65 percent), Mideast (?3.32 percent), and Southeast (+3.64 percent). Four major industry sectors (Agriculture, Mining, Construction, and Government) declined in relative importance in all eight regions. Five major industry sectors (TCPU, Retail Trade, Wholesale Trade, FIRE, and Services) expanded in relative importance. Somewhat surprisingly, Manufacturing output expanded for the U.S. as a whole and for six of the eight regions. The perception of decline in the relative importance of manufacturing in the U.S. is clearly based on the dramatic declines in the once dominant manufacturing base of the Mideast and Great Lakes regions.     

Dynamics of the U.S. interstate migration system, 1975-1992

This note further develops an analysis of the U.S. interstate migration system by K.E. McHugh and P. Gober. Specifically, it uses annual state-to-state migration flow data from Internal Revenue Service for the period 1975-1992 to analyze migration trends. Some modifications to earlier conclusions are suggested. "First the note concludes that the emergence of a new pattern of population redistribution in the U.S. in the 1980s, as reported by McHugh and Gober, was indeed significant, but that it was transitory. Second, the note's analysis does not support McHugh and Gober's conclusion of a fairly strong inverse relationship between migration effectiveness and economic expansions and contractions."     

Short-term dynamics of the U.S. interstate migration system, 1980-1988

"This paper identifies short-term fluctuations in the [U.S.] interstate migration system using annual state-to-state migration flow data from Internal Revenue Service (IRS) records for the period, 1980 to 1988. Measures of migration efficiency are employed to indicate the net redistribution of population between states relative to the size of underlying gross interstate flows. Three findings stand out: (1) migration was more effective in redistributing the population in years of economic retrenchment than during periods of growth and expansion, (2) the dominant pattern of population redistribution shifted from a core-periphery configuration evident in the 1970s and early 1980s to a bi-coastal distribution by the mid-1980s, and (3) the most dramatic event of the 1980s was the oil glut and decline in oil prices and profits which ravaged the economies of energy states in the West South Central and Mountain regions....Overall, results demonstrate the high degree of temporal and spatial volatility in the U.S. interstate migration system."     

Patterns of Broadband Efficiency in the U.S

Data envelopment analysis is used to assess the efficiency of broadband Internet adoption and use in the U.S. Analyses at the state level from 2005 to 2007 suggest that broadband adoption and use is not equally efficient across the U.S. states. Although the instantaneous efficiencies are relatively high for many states, the changes in total factor productivity suggest that the efficiency of broadband adoption and use still increases over time. Moreover, it is observed that efficiency values are often spatially autocorrelated, which suggests spatial dependency from spillovers or interstate competition. This leads to a particular spatial diffusion pattern in broadband adoption. Although states have different strategies in support of broadband expansion they need to identify their shortcomings and use the appropriate mix of inputs (and outputs) to improve their efficiencies.     

Using moving-industry data to depict U.S. migration patterns

"Migration analysis is hindered by the lack of up-to-date migration data. This paper examines the feasibility of using information from the American Moving Conference (AMC), the trade organization of the moving industry, to develop timely estimates of gross in- and out-migration and net migration rates at the state level. When adjusted for the spatially varying size of migrant households and the spatially varying market share of the professional moving industry, the number of AMC inbound and outbound shipments provides useful, but slightly imperfect, estimates of migration in 1990 and 1991. Viewed as a time series, adjusted AMC shipment data accurately reveal the major migration stories of the last decade. AMC-based estimates for 1992, 1993, and 1994 provide a picture of state in- and out-migration for years in which official data are not yet available."     

The Impact of the Maquiladora Industry on U.S. Border Cities

For decades, the maquiladora industry has been a major economic engine along the U.S.–Mexico border. Since the 1970s, researchers have analyzed how the maquiladora industry affects cities along both sides of the border. Hanson produced the first comprehensive study on the impact of the maquiladoras on U.S. border cities, considering the effects of in‐bond plants on both employment and wages. His estimates became useful rules of thumb for the entire U.S.–Mexico border; however, they have become dated. Using Hanson's framework, we estimate the maquiladora industry impact on U.S. border cities from 1990 to 2006. We find that a 10 percent increase in maquiladora production leads to a 0.5 to 0.9 percent increase in employment. We also find large differences among individual border cities. Furthermore, we estimate the cross‐border maquiladora impacts before and after 2001 when border security begins to rise, and the global low‐wage competition intensified after China joined the World Trade Organization. Empirical results indicate that U.S. border cities are less responsive to growth in maquiladora production from 2001 to 2006 than in the earlier period; however, when looking into specific sectors, we find that U.S. border city employment in service sectors is more responsive post‐2001.     

The Spatial Structure of Large U. S. Law Firms

Large law firms exert a disproportionate influence over the structure and practice of the legal profession. The spatial structure of these corporations, including the distribution of headquarters and branch offices and their interlinkages, is poorly understood. This paper explores the geography of domestic employment among the largest U. S. 500 law firms using linkage analysis. It highlights the concentration of such firms in large cities and the particular importance of New York and Washington, D. C. In the international arena, U. S. law firms are highly influential. The paper examines the spatial distribution of overseas employment by large U. S. law firms and utilizes input-output analysis to explore the domestic employment impacts of foreign legal services exports.