Causes of Decadal Climate Variability over the North Pacific and North America

The cause of decadal climate variability over the North Pacific Ocean and North America is investigated by the analysis of data from a multidecadal integration with a state-of-the-art coupled ocean-atmosphere model and observations. About one-third of the low-frequency climate variability in the region of interest can be attributed to a cycle involving unstable air-sea interactions between the subtropical gyre circulation in the North Pacific and the Aleutian low-pressure system. The existence of this cycle provides a basis for long-range climate forecasting over the western United States at decadal time scales.     

Enhanced Atmospheric Circulation over North America During the Early Holocene: Evidence from Lake Superior

Profiles of grain sizes in five cores recovered from Lake Superior show that grain size increased with burial depth to the postglacial-glacial contact. The results reflect a substantial reduction in bottom-current velocity and the corresponding wind velocity from 9500 to 6500 years ago.     

国内外农业标准化发展现状与分析

随着经济全球化和贸易自由化进程的加快以及我国加入世界贸易组织,农业标准化势在必行。本文阐述了国内外农业标准化生产管理现状,并对两者之间的差距进行了分析,最后指出推动中国农业标准化生产管理需要采取的措施。     

DNA from pre-Clovis human coprolites in Oregon, North America

The timing of the first human migration into the Americas and its relation to the appearance of the Clovis technological complex in North America at about 11,000 to 10,800 radiocarbon years before the present (14C years B.P.) remains contentious. We establish that humans were present at Paisley 5 Mile Point Caves, in south-central Oregon, by 12,300 14C years B.P., through the recovery of human mitochondrial DNA (mtDNA) from coprolites, directly dated by accelerator mass spectrometry. The mtDNA corresponds to Native American founding haplogroups A2 and B2. The dates of the coprolites are >1000 14C years earlier than currently accepted dates for the Clovis complex.     

国内外离心泵运行管理标准差异分析

为了降低离心泵故障率,减少维护成本,全面梳理了国内外离心泵运行管理标准。从离心泵设计安装、运行管理和维护修理3个方面,深入研究了国内外离心泵技术标准的差异。系统阐述了俄罗斯标准、美国标准和ISO标准的先进性,包括泵与出入口管道的连接要求、泵房通风系统控制逻辑关系、泵基础下陷情况监测、泵紧急停车的情形、泵检测维修周期以及泵轴承箱和泵轴的振动幅度和速度限制等。建议借鉴国外相关标准的先进理念,加强标准制修订工作,以提高我国离心泵的运行管理标准水平。（表7,参6）     

Genomic heterogeneity of AIDS retroviral isolates from North America and Zaire

In an analysis of the genomic variation of AIDS retroviral isolates from patients living in New York, Alabama, and Zaire, restriction maps were constructed by using seven enzymes, each known to cleave the proviral DNA more than once, in conjunction with Southern blot analysis. The maps of LAV, HTLV-III, and ARV-2 as deduced from their published nucleotide sequences were included in this analysis. The results demonstrated that (i) several "signature" restriction sites were common to all isolates; (ii) with the exception of LAV and HTLV-III, the North American and European isolates were all different from one another and showed no geographical specificity; (iii) the African isolates as a group were more diverse than those from North America and Europe; and (iv) the genomic variability was concentrated within the env gene.     

辽宁省引种班克松的种源选择

对从北美引进的9个种源班克松所做的17a的试验结果表明:班克松是适合辽宁地区的一个优良速生树种,在各个生长时期的生长表现都要好于乡土速生针叶树种———樟子松。班克松不同种源之间的生长状况存在着较大差异,班克松各种源树高、胸径、材积生长在2年生苗期、造林后5年生、8年生、15年生时差异都达到极显著水平。2、8号种源班克松15年生时的生长表现最佳,它们的树高分别比9个种源平均高大4.8%、4.8%,胸径分别比9个种源平均胸径大8.2%、4.9%,材积分别比9个种源平均材积大21.1%、13.5%;而3、5号种源班克松15年生时的生长表现最差。班克松的树高、胸径、材积生长状况与纬度因子呈显著负相关,来自北美北纬46°附近的班克松种源是最适合辽宁地区引种的优良种源,而远离北纬46°及越向高纬度地区的班克松种源在该区表现较差。建议辽宁地区引进北美北纬46°附近的班克松种源,并建立起优良的班克松种子园。     

北美种子质量控制体系

一、北美种子质量控制的历史与现状在美国和加拿大，种子质量控制的历史可追溯到１９世纪初期，当由州立大学和政府实验站培育出第一个新品种时，相应的新品种种子质量控制也应运而生。在此之前，美、加大部分大田作物都是由其他国家的作物品种衍生而来，每当新品种诞生就被随机分发到农民手中，这些品种常常被丢失或混杂。１９００—１９２０年间，全美各州纷纷成立组织，向农民分发“学院培育”的品种，这些组织很快发展成州立实验站，进而又成为作物改良机构或种子质量控制组织机构———种子认证机构。从２０世纪２０—４０年代，在全美…     

Radiocarbon dating and archeology in North America

The history of the development of a radiocarbon chronology shows how the establishment of the times of events and the order of them has greatly improved the understanding of prehistory in North America. This is true also of other parts of the world. Too little has been said of existing discordance between archeologically determined sequences, and interregional associations, and the radiocarbon chronology. It does appear that these will be resolved as additional dates are added and as the results become more finely calibrated so that secular variations may be accounted for. The collaborative aspect of the venture was apparent at the outset. Nevertheless no one expects an archeologist to delve into nuclear physics and geochemistry, and vice versa. There is great need, nevertheless, for the man in the laboratory to comprehend the difficulties of sample collecting and of judgement of the significance of the source of organic matter to be dated. At the same time, the archeologist must become more familiar with the importance of the various steps in the processing of the sample and with, what is most vital, interpretation of the significance of the numbers that appear on the counters.     

The first glacial maximum in North America

Despite marine evidence for at least 50 Pliocene-Pleistocene ice sheet advances, only the most recent one has been accurately reconstructed from terrestrial evidence, because there are few techniques for dating older glacial deposits. Here we show that the cosmic ray-produced nuclides beryllium-10 and aluminum-26 can be used to date tills that overlie paleosols.     

论服务业对外直接投资对母国国内投资的影响

服务业对外直接投资对一国经济业绩影响的核心问题在于对外投资是否以牺牲国内投资为代价。当母国国内的资源已充分利用时，国内多余资本将会构成通货膨胀的压力，因而这时资本转移出境是有好处的。当母国国内资源尚未充分利用，但发生结构性剩余时，这时的对外直接投资还要取决于国内外的投资利润率大小。     

国内外农业大数据发展的现状与存在的问题

【目的 】 为促进农业大数据在我国农业生产中的应用,提高农业生产效率和质量。 【方法 】 文章首先通过梳理大数据相关文献,对农业大数据理论的提出和发展进行回顾,总结大数据在农业中的重要作用;其次,对我国以及美国、以色列、日本这3个主要发达国家的农业大数据发展现状进行分析,进而总结了国内外农业大数据的特点并归纳国内外农业大数据存在的问题。 【结果/结论 】 我国需借鉴国外先进的农业生产模式,从农业规范化、精准化、智能化三方面发展,这将对我国农业大数据在农业生产中的应用具有重要指导作用,从而提高生产效率、减少浪费、充分利用有限的农业资源,为我国粮食安全提供保障。     

场外债券交易信息强制披露机制探悉——以北美债券市场为例

场外债券市场成为债券交易的主板市场以来,加强场外市场交易信息透明度的呼声日益提高。本文介绍了美国、加拿大在债券市场交易信息强制披露方面的做法,以期对我国债券市场的建设有所启示。     

北美大豆食品现状

一、大豆食品在北美的历史大豆在中国有四五千年历史，大约在公元前164年中国发明了豆奶和豆腐。900年后，这些大豆食品加工方法传入日本和太平洋周边国家，大约在1712年大豆进入欧洲、CalVonLinne′给大豆定学名为Glycinemax（意思是带有大根瘤的田野坚果），然而欧洲的土壤和气候条件限制了大豆的生产。1764年大豆传到北美，1年后在佐治亚州种植，随着栽培技术和机械收获技术的发展，大豆作为动物饲料和食用油在北美逐步发展起来。1998／99年度全世界大豆产品超过1.56亿t，85％用于榨油和豆粕，10％用于食品（在美国只有大约1％），5％…     

Aedes albopictus in North America: probable introduction in used tires from northern Asia

North American strains of Aedes albopictus, an Asian mosquito recently introduced into the Western Hemisphere, exhibit photoperiodic sensitivity and cold-hardiness characteristics similar to strains originating from temperate zone Asia. Trade statistics for used tire imports, the most likely mode of introduction, also indicate a north Asian origin. Aedes albopictus, an important vector of dengue and a potential vector of many other arboviral diseases, may therefore have the capability of infesting much of temperate North America.     

The mantle flow field beneath western North America

Although motions at the surface of tectonic plates are well determined, the accompanying horizontal mantle flow is not. We have combined observations of surface deformation and upper mantle seismic anisotropy to estimate this flow field for western North America. We find that the mantle velocity is 5.5 +/- 1.5 centimeters per year due east in a hot spot reference frame, nearly opposite to the direction of North American plate motion (west-southwest). The flow is only weakly coupled to the motion of the surface plate, producing a small drag force. This flow field is probably due to heterogeneity in mantle density associated with the former Farallon oceanic plate beneath North America.