萨拉乌苏动物组合对Heinrich事件的反映

萨拉乌苏动物组合包括下部的萨拉乌苏动物群和上部城川动物群,前者含有水牛和古菱齿象等化石,属于晚更新世中期,环境较为温凉湿润;后者以野驴和披毛犀为主,属于晚更新世晚期,代表较干冷的气候环境。综合两者的动物组合、测年结果及其生态特点,显示前者应该是末次冰期中期的温凉湿润环境,而后者则应为末次冰盛期的前夜,应该是另一次Heinrich事件H2的动物组合。     

Last Glacial mammals in South America: a new scenario from the Tarija Basin (Bolivia)

The chronology, sedimentary history, and paleoecology of the Tarija Basin (Bolivia), one of the richest Pleistocene mammalian sites in South America, are revised here based on a multidisciplinary study, including stratigraphy, sedimentology, geomorphology, paleontology, isotope geochemistry, and ¹⁴C geochronology. Previous studies have indicated a Middle Pleistocene age for this classic locality. We have been able to obtain a series of ¹⁴C dates encompassing all the fossil-bearing sequences previously studied in the Tarija Basin. The dated layers range in age from about 44,000 to 21,000 radiocarbon years before present (BP), indicating that the Tarija fauna is much younger than previously thought. Glacial advances correlated to marine isotopic stages (MIS) 4 and 2 (ca. 62 and 20 ka BP, respectively) are also documented at the base and at the very top of the Tarija–Padcaya succession, respectively, indicating that the Bolivian Altiplano was not dry but sustained an ice cap during the Last Glacial Maximum. The results of this multidisciplinary study enable us to redefine the chronological limits of the Tarija sequence and of its faunal assemblage and to shift this paleontological, paleoclimatological, and paleoecological framework to the time interval from MIS 4 to MIS 2.     

“马坝人”与“石峡文化”──纪念“马坝人”头骨化石发现40周年

本文以科普形式介绍在广东曲江马坝镇发现的“马坝人”古人类头骨化石和附近新石器时代“石峡文化”情况。并探讨二者承前启后关系。     

武汉阳逻砾石层ESR地层年代学研究

武汉"阳逻砾石层"是长江中下游新生代的一个重要的岩石地层单位,其形成年代一直是地质和地理学者关注的重要问题。为了更深入地探讨这一问题,在它的两个典型的剖面中采集了8个样品进行ESR地质年代测试,测试结果表明,阳逻砾石层形成于新近纪早更新世中晚期。将本次ESR测年数据与前人的热释光的测年数据、江汉平原西缘和北缘相同岩石地层层位和相同地貌位置的砾石层的测年数据、长江中下游网纹砾石层的测年数据比较发现,它们具有较好的一致性。     

中国黄土释光测年与应用:过去、现在与未来

中国黄土释光测年走过了近40年的历程,这对于推动释光测年技术的进步和黄土古气候古环境研究的深入有重要意义。本文针对中国黄土(以黄土高原为主),简要回顾了以多片法混合矿物热释光(TL)和红外释光(IRSL)测年技术为主的早期(20世纪70年代末期至21世纪第一个十年初期)探索阶段的发展,重点阐述了以成熟的单片再生剂量(SAR)法石英光释光(OSL)技术和延长测年年限的多种方法并存为特征的目前(21世纪以来)研究进展。同时,系统论述了释光测年技术在晚更新世以来中国黄土古气候古环境研究中的意义,如在年代标尺建立、粉尘堆积速率变化重建、地层对比与划分、轨道和亚轨道尺度气候演变与气候事件揭示等方面的应用。另外,也对将来中国黄土释光测年技术的发展方向和其在古气候古环境研究领域的应用前景进行了简单展望。     

西藏日土县班公错地区晚更新世晚期植物群与古气候探讨

本文通过孢粉分析及¹⁴C年龄测定,恢复西藏班公错地区晚更新世晚期的植物群。约在距今40,000—42,000年（a）期间,班公错盆地曾以半荒漠-草原-荒漠交替出现;山地上有少量乔木植物。古气候比现今湿润、气温偏高,以距今3.6—2.8 × 10⁴年（a）期间的温湿最明显。     

更新世黄土高原强烈侵蚀期发生的环境条件

在更新世,黄土高原经历了若干堆积-侵蚀旋回。其中黄土堆积主要发生在冷干期,而强烈土壤侵蚀发生的环境条件至今尚无统一认识,其确定对了解黄土高原地貌的演化过程和更新世侵蚀期的求得均具有重要意义。通过对比黄土高原侵蚀模数分布图与新构造运动分区图,得出侵蚀模数高值区与构造抬升强烈区并不吻合,推断黄土高原侵蚀期发生的主要原因不是构造抬升。在野外考察中,寻找了多个侵蚀面,并与邻近较为完整的黄土-古土壤剖面进行比照,发现侵蚀面主要存在于黄土层上部,其上覆的古土壤层一般保存完整,说明土壤侵蚀主要发生在黄土层,即气候由冷干向暖湿的过渡时期。这一结论为求取黄土高原第四纪侵蚀期提供了理论依据。     

四氟乙烷（HFC—134a）急性,亚急性毒性的研究

本文研究了四氟乙烷（ＨＦＣ－１３４ａ）和二氟二氯甲烷（ＣＦＣ－１３，氟利昂１２）的急性．亚急性毒性，给大鼠吸入高浓度ＨＦＣ－１３４ａ或ＣＦＣ－１２，观察和记录体重，心电图，血象，生化指标，脏器系数和病理组织学变化，结果显示：实验动物均无病理改变，无死亡，二者的毒性相近，属基本无毒，因此以毒性为指标，ＨＦＣ－１３４ａ可作为ＣＦＣ－１２的替代品。     

某电容器加速贮存寿命试验设计研究

加速贮存寿命试验设计是设计一个最优的试验指导方案.一个好的试验方案可以提高模型参数估计精度和寿命外推的准确性,可以缩短试验时间、提高试验效率.本文在探讨该电容器的失效机理分析的基础上,在从应力加载方式、应力类型、水平、参试样品、截尾方式、测试、判据等多方面开展试验方案的设计.     

The puzzle of North America's Late Pleistocene megafaunal extinction patterns: Test of new explanation yields unexpected results

Although Late Pleistocene extinctions disproportionately affected larger mammalian species, numerous smaller species were also lost. To date, no satisfactory explanation has been presented to account for this pattern. Beginning with the assumption that human predation caused the extinctions, we offer and test the first such explanatory hypothesis, which is predicated on considering more realistic functional response forms (i.e., those that allow for predator interference or prey sharing). We then test the hypothesis via a one-predator, six-prey ecological model that maintains transparency, minimalism of design, and maximal constraint of parameters. Results indicate that altering assumptions about one cornerstone of ecological modeling (i.e., functional response) fails to produce qualitative differences in survival–extinction outcomes—even in conjunction with a wide range of capture efficiency permutations. This unexpected finding suggests that no reasonable form of predation alone is capable of producing the survival–extinction pattern observed. We conclude that the matter of causation and the conclusions of previous Late Pleistocene extinction models remain far less certain than many have assumed.