Test of magnetic susceptibility and grain-size age models of loess

Ages of the stratigraphic boundary MIS1/2 and MIS3/4 of the Yuanbu loess section in Linxia are used as the basis of the nodal control age. The age of MIS1/2 and MIS3/4 are obtained from the latest international research result—the climatic events recorded in the stalagmite in the Hulu Cave in Nanjing, that MIS1/2 is 11.5 kaB.P. and MIS3/4 is 59.8 kaB.P.. The ages of the two climatic events contain three nodal age control models (Model 1: 0 kaB.P.—59.8 kaB.P.; Model 2: 0 kaB.P.—11.5 kaB.P. and 11.5 kaB.P.—59.8 kaB.P.; Model 3: 11.5 kaB.P.—59.8 kaB.P.), which are used as the nodal control age separately. The deposition times of various stratigraphic horizons are calculated by using the magnetic susceptibility age model and grain-size age model, and then compared with each other. In addition, the AMS14C age, OSL age and the ages of YD and H events are compared with the ages of the corresponding horizons calculated by the three models of nodal control ages. From the analyses of lithologic characters and climatic stages it has been found that both the magnetic susceptibility age model and the grain-size age model have some defects. Because the accurate control ages are selected as the nodal points of the glacial period or interglacial period, the stratigraphic deposition times determined by the high resolution of magnetic susceptibility age model and grain-size age model approximate to the actual ages. As for the relative accuracy of the two age models, the magnetic susceptibility age model is more accurate than the grain-size age model.     

Test of magnetic susceptibility and grain-size age models of loess

Ages of the stratigraphic boundary MIS1/2 and MIS3/4 of the Yuanbu loess section in Linxia are used as the basis of the nodal control age. The age of MIS1/2 and MIS3/4 are obtained from the latest international research result—the climatic events recorded in the stalagmite in the Hulu Cave in Nanjing, that MIS1/2 is 11.5 kaB.P. and MIS3/4 is 59.8 kaB.P.. The ages of the two climatic events contain three nodal age control models (Model 1: 0 kaB.P.—59.8 kaB.P.; Model 2: 0 kaB.P.—11.5 kaB.P. and 11.5 kaB.P.—59.8 kaB.P.; Model 3: 11.5 kaB.P.—59.8 kaB.P.), which are used as the nodal control age separately. The deposition times of various stratigraphic horizons are calculated by using the magnetic susceptibility age model and grain-size age model, and then compared with each other. In addition, the AMS14C age, OSL age and the ages of YD and H events are compared with the ages of the corresponding horizons calculated by the three models of nodal control ages. From the analyses of lithologic characters and climatic stages it has been found that both the magnetic susceptibility age model and the grain-size age model have some defects. Because the accurate control ages are selected as the nodal points of the glacial period or interglacial period, the stratigraphic deposition times determined by the high resolution of magnetic susceptibility age model and grain-size age model approximate to the actual ages. As for the relative accuracy of the two age models, the magnetic susceptibility age model is more accurate than the grain-size age model.     

～4.1 Ga xenocrystal zircon from Ordovician volcanic rocks in western part of North Qinlin80rosenic Belt

High-precision U-Pb dating by in situ LA-ICP-MS yields an age of 4079±5 Ma for a xenocrystal zircon from Ordovician volcanics of the Caotangou Group in western part of the North Qinling Orogenic Belt. As a result, the North Qinling Orogenic Belt becomes one of a few localities in the world that contain Hadean age records （4276±6 Ma and 4404±8 Ma detrital zircons from Jack Hill of the Yilgarn craton, 4016 Ma Acasta gneisses of the Wopmay Orogeny and Burang quartzite with detrital zircon of 4103 Ma in Tibet）. It is also the first report of the Hadean age in Phanerozoic volcanics. The finding of the 4.1 Ga xenocrystal zircon provides not only the geochronological record of the oldest crustal materials in China, but also the condition for further search for rocks forming in the region during the early time of the Earth＇s evolution. Thirty-six zircon U-Pb dates from the Ordovician volcanic rocks are subgrouped into seven generations that represent different tectono-magmatic events in the North Qinling Orogenic Belt. Among them, two periods of 0.9--1.5 Ga and 0.4--0.5 Ga are consistent with Mesoproterozoic and Early Paleozoic orogenies, respectively.     

信息时代我国公共图书馆信息咨询服务研究

随着网络信息技术和信息市场的飞速发展,我国的信息咨询服务业也逐渐发展了起来,信息咨询工作已经成为现代图书馆的一项核心职能。但由于各种原因的影响,我国公共图书馆的信息咨询服务工作仍不尽如人意。通过分析信息时代我国公共图书馆信息咨询工作的现状和不足,提出了提高信息咨询服务工作水平的对策。     

试论信息时代高校师生角色的转变

信息时代高等教育的教学目标是培养适应社会发展、具有良好科学素养的人才,实现这一目标必须依靠教师的力量和学生的努力。师生以何种角色来面对这一形势,是培养学生创新能力的关键。文章阐述了信息时代下高校师生角色转换的必要性和可能性,论述师生传统角色对高校发展的制约和在信息时代师生应该具有的角色特征,提出了信息时代高校师生角色转换的策略。     

胡适出使英国始末

1937年9月-1942年8月，胡适在美国度过了5年外交生涯。任大使期间，在经费困难和国际环境险恶的情况下，他一方面与美国上层频繁接触，获得了美国的两笔贷款，为抗战筹措资金；另一方面豁出性命讲演，宣传蒋介石和国民政府的对日政策，为抗日作舆论宣传。但由于客观环境的限制和他人的误解，以及与宋子文之间的龃龉，最终被蒋介石免职。     

网络教学——信息时代的教育新趋势

本文从信息时代对专业型人才和综合型人才的需求出发，结合人才培养模式的发展要求，通过对计算机技术及网络通讯技术的特点分析，提出了开展网络教学是信息时代教育模式发展的新趋势；同时就目前开展网络教学需要关注的几个问题提出了自己的见解。     

对当代政治抒情诗的探讨

盛行于20世纪50年代末60年代初的政治抒情诗，既是50年代颂诗中政治抒情诗的发展，又是当时国内外错综复杂的政治斗争与社会生活的反映。作为一种特定历史时期的艺术样式，我们在新的历史高度将这些诗作为一种特殊的话语类型进行考察，能得到全新的启悟与感受。     

U型膨胀剂对防水混凝土结构开裂的抑制作用

钢筋砼抗渗结构的开裂是渗漏的主要原因，这个带有普遍性的问题长期困扰着广大施工技术人员。在普通砼中掺入适量的U型膨胀剂，减小了砼结构开裂的可能性，提高了砼的抗渗能力，为防水砼的施工提供一种借鉴的方法。     

论明末清初的遗民词

遗民词并不是明清之际词人首创。然而 ,还从来没有哪个时代遗民词创作 ,能达到明末清初的高度 ;没有哪个时代遗民词的创作 ,能像明末清初一样有着明确、统一的主题 ;没有哪个时代的遗民词 ,在政治内涵的深度和广度上 ,能与明末清初媲美。可以毫不夸大地说 ,明末清初的遗民词成就是巨大的 ,在中国文学史上前无古人。这是我们民族一份极为珍贵的文学遗产