Cd、Pb单一污染对龙须草干物质积累的影响

通过盆栽试验研究了Cd、Pb单一污染对龙须草生长全期干物质积累的影响。结果表明,在成熟期以前,Cd、Pb低浓度(不高于5mgCd/kg土)刺激能够促进龙须草植株干物质积累,高浓度(不低于200mgPb/kg土)刺激对龙须草干物质积累有抑制作用。被Cd、Pb污染的龙须草在成熟期时干物质积累总量比前一时期略微减小。Cd、Pb的临界浓度分别为5mgCd/kg土和200mgPb/kg土,表明龙须草干物质积累对Cd污染较Pb污染敏感。     

R~2上完备性定理的等价性循环证明

给出了R2上五个完备性定理的循环证明,从理论上更详细地说明了定理之间的等价性.     

清代徽成盆地农业开发问题研究

徽成盆地自古是川蜀门户,地理位置极其重要.该区自然条件优越,水资源丰富,为历代统治者所重视.在清代,徽成盆地的农业开发呈现出新的特色,外来人口的迁入和新作物的栽培与推广使得农业开发的广度和深度都进入了新的阶段.研究其经验、教训,对今天的徽成盆地开发有非常重要的借鉴作用.     

论全球化中烟草控制的国际政策协调

随着人们对生命和健康的关注,许多新的与烟草控制相关的国际法原则、规范和制度在国际关系和国际实践中被确立,影响到烟草行业的各个方面.一些新的与烟草控制相关的国际法分支不断涌现,呈现出十分活跃的发展态势.这些分支自成体系,当各分支具体规则发生交叉时,出现不协调和冲突的可能性增加.为此,与烟草控制相关的国际法规则的协调化需要尽快完成,但其中的难度极大,有许多曲折的道路要走.     

加入WTO与中国烟草企业的股份制改革

烟草业在中国的国民经济中具有重要的地位 ,其发展对中国经济的影响不言而喻。从总体上看 ,中国烟草业现阶段已形成相对庞大的产业规模和较为完整的产业体系 ,产品也有一定的市场竞争力。但业内人士认为 ,在繁荣的背后 ,中国烟草业在迎接国内市场国际化的竞争中显得十分脆弱 ,国际竞争力令人担忧。本文针对入世带来的新问题、新形势 ,从经济和法律的角度对烟草企业的股份制改革的必要性进行分析 ,结合国内外股份企业发展的实践论证烟草企业进行股份制改革的可行性 ,并建议以红塔为试点对国内烟草大企业的进行股份制改制 ,通过设立烟草股份公司发行股票上市 ,吸纳资金 ,壮大企业规模 ,以构造我国烟草业的航空母舰 ,抵御外来竞争的压力。     

“斯密型增长”还是“熊彼特型增长”——区域结构视角的我国经济增长模式分析

对我国经济增长主要依赖要素投入增加还是技术进步,国内外学术界尚未取得一致结论。鉴于我国区域经济发展差距巨大,对2000~2010年省际经济增长数据进行Malmquist指数分解和聚类分析,结果表明：近年来我国经济增长效率存在着显著的区域差异,且不存在某种占据主导地位的模式;空间布局上基本呈现出东部地区在效率方面优于西部、西部又优于中部的特征。因此,笼统地讨论我国经济的增长模式缺乏内在逻辑一致性,而要实现经济增长方式的转变,则必须分区域实施针对性战略,同时强化市场制度建设以提高全国市场的统一程度。     

植物硝态氮营养

硝态氮是氮素形态之一,植物体对硝酸氮的吸收是由一种可以产生电的协同运输机制来驱动的,硝酸氮的同化是在硝酸还原酶和亚硝酸还原酶的作用下还原成NH4 。硝态氮的一般营养功能可以通过近些年来的科技文献表现出来,主要有增施硝态氮可以提高作物的产量;通过控制硝态氮的数量可以防止硝态氮在蔬菜中积累,从而改善蔬菜的品质。另外,硝态氮在土壤中的积累与淋失对环境所造成的污染严重,本文将提出一些措施进行防治。硝态氮能促进铵态氮的吸收,平衡吸收氮素利于植物的生长发育。另外,硝态氮研究也存在不足,其中硝态氮在树木中研究还不算深入。     

Depression,anxiety, and tobacco use: Overlapping impediments to sleep in a national sample of college students

ABSTRACT

Objectives: To examine how tobacco use and depression/anxiety disorders are related to disturbed sleep in college students. Participants: 85,138 undergraduate respondents (66.3% female, 74.5% white, non-Hispanic, ages 18–25) from the Spring 2011 American College Health Association–National College Health Assessment II database. Methods: Multivariate analyses of tobacco use (none, intermediate, daily) and mental health (diagnosed and/or symptomatic depression or anxiety) were used to predict sleep disturbance. Results: Daily tobacco use was associated with more sleep problems than binge drinking, illegal drug use, obesity, gender, and working >20 hours/week. Students with depression or anxiety reported more sleep disturbances than individuals without either disorder, and tobacco use in this population was associated with the most sleep problems. Conclusions: Tobacco use and depression/anxiety disorders are both independently associated with more sleep problems in college students. Students with depression and/or anxiety are more likely to be daily tobacco users, which likely exacerbates their sleep problems.     

Cigarette Smoking Among Korean International College Students in the United States

Abstract

Objective and Participants: This study explored (1) the prevalence of cigarette smoking among South Korean international college students in the United States, (2) differences in smoking between on- and off-campus living arrangements, and (3) predictors of an increase in smoking over time in the United States Methods: An online survey was completed by 1,201 students at 52 4-year US universities (34% response rate). Results: The overall smoking prevalence was 43.5%. The smoking rate (29.0%) of female students was higher than that (4%) of female college students in South Korea. Sex, living place, living situation, length of stay as a student in the United States, home smoking rules, campus-wide tobacco-free policies, and levels of acculturative stress, anxiety, and depression were significantly associated with an increase in smoking (p < .05). Conclusions: Given the high smoking prevalence among the South Korean students on US college campuses, targeted prevention efforts for these students may be warranted.     

A Systematic Analysis of College Substance Use Policies

College substance use policies provide guidelines for student behavior and influence campus culture. Although they are the primary environmental strategy to address campus substance use, policies have not been systematically compared and studied. We constructed a systematic review method to examine the accessibility, comprehensiveness, enforcement procedures, and clarity of college substance use policies. We developed an objective evaluation scheme for each of these 4 dimensions and then applied it to documented substance use policies from a sample of colleges and universities (N = 24). Policies were found to vary considerably but tended to specify compliance with local laws and emphasize student health and well-being. The next stage of campus policy review should examine actual implementation, evaluate potential differentiating factors among institutions, and assess the influence of policy on campus climate and student outcomes.