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971.
周口店田园洞古人类化石点地层学研究及与山顶洞的对比   总被引:8,自引:1,他引:7  
田园洞主体堆积厚度约2.5m,其动物群可分为上、下两个组合:上部组合物种多样性丰富,化石被啮齿类严重啮咬;下部组合化石种类单调,以鹿类和绵羊类为主,但化石丰富,极少有啮齿类咬痕。人类化石发现于下部组合;东洋界动物主要出现在上部组合,例如猕猴、猪獾、果子狸和鬣羚等。而马鹿和绵羊只出现于下部组合。沟齿鼯鼠和豪猪在下部组合开始出现,但主要发现于上部组合。梅花鹿是田园洞的优势种,在各个阶段都出现。通过统计比较,发现山顶洞3个地层单元(上室、下室和下窨)中所含化石属种基本一致,代表同一个动物群。尽管田园洞动物群中尚未发现可靠绝灭种类,但却有10种地区绝灭种,它与现生动物群有一定差异;而在堆积物特征及化石组合方面,与周口店山顶洞的更为接近。在田园洞和山顶洞出现的沟齿鼯鼠、猪獾、果子狸及鬣羚等是各自在华北地区的最早记录,可能代表了更新世末期自南而北的动物迁徙事件。  相似文献   
972.
岷江上游不同景观结构小流域水量平衡的比较   总被引:1,自引:0,他引:1  
研究了1988~2002年岷江上游两个小流域(镇江关流域和黑水河流域)不同景观结构(土地覆盖、海拔、坡度、斑块密度、最大斑块指数等)对水量平衡的影响.基于两个流域土地覆盖类型、1988~2002年多年平均降水量和蒸散量的空间分布、两个流域土地覆盖类型同期多年平均径流深度的数据,得到不同土地覆盖类型的海拔、坡度、坡向与降雨、蒸散、径流的关系.结果表明,两个流域有林地海拔、坡度、坡向的不同导致其降水、蒸散降水比、径流降水比各异;两个流域草地水量平衡对景观格局的响应模式与有林地基本一致;由于黑水河流域的耕地分布在干旱河谷中,其蒸散量远远大于降水量,耕地本身的景观结构(坡向、坡度,斑块密度)并不对其水量平衡产生影响,这一点与镇江关完全不同.  相似文献   
973.
萌蘖调控对辽东栎留存萌生株生长与结实的影响   总被引:3,自引:1,他引:2  
比较了不同调控措施对岷江上游辽东栎萌生灌丛生长与结实的影响.结果表明,人为调控对辽东栎萌生灌丛本生长阶段的高生长与有性繁殖有着显著影响.各调控措施对辽东栎灌丛萌生株的基径增长未产生明显影响;保留2支和3支萌生株的丛高生长优势明显.调控丛的新生枝数量、总长度、总生物量较未调控前有较大增加,保留2支萌生株的丛类型增加得尤为显著;叶片数量、叶片总生物量与未调控前相比增加明显,叶片面积按保留萌生株数量由多到少逐渐变小.调控后,每丛保留3支萌生株的丛产生的种子最多,但自然状态丛种子单粒重最大.  相似文献   
974.
The role of arm motion on the performance of the standing long jump was investigated. Three males performed a series of jumps with free (JFA) and with restricted (JRA) arm motion to determine if arm swing improves jumping distance. The subjects jumped off a force platform and the motion of the body segments were recorded with a four-camera, passive motion-capture system. Jumping performance was defined as the horizontal displacement of the toe between the initial and landing (TD) positions. The subjects jumped 21.2% further on an average with arm movement (2.09±0.03 m) than without (1.72±0.03 m). Seventy-one percent of the increase in performance in JFA was attributable to a 12.7% increase in the take-off (TO) velocity of the center of gravity (CG). Increases in the horizontal displacement of the CG before TO and in the horizontal position of the toe with respect to the CG at TD accounted for the remaining 29% of the improvement in jumping distance. The added balance and control provided by the arms throughout the jumping motion contributed to performance improvement in JFA. The subjects were able to remedy excessive forward rotation about the CG by swinging the arms backwards during the flight phase. Without the freedom to swing the arms during flight, the subjects had to eliminate any excessive forward rotation while still in contact with the ground. This tendency in JRA was manifest in the premature decline in the vertical ground reaction force (VGRF) and the development of a counterproductive backward-rotating moment about the CG just before TO.  相似文献   
975.
In this study, we screened serum samples for transient hyperphosphatasemia (TH) using cellulose acetate membrane electrophoresis over a period of 3 years. In the patients found to suffer from TH, we examined the relationship between the clinical condition and viral infection. The frequency of TH was 0.26%, and all of the cases detected were in infants or young children. The female to male ratio of TH was 1.29/1. While there was no clear seasonal fluctuation or periodicity in the appearance of TH, two peaks were recognized in spring and autumn. Research on the clinical manifestations clarified that most of the TH cases had infectious diseases of the upper airways accompanied by symptoms of fever and diarrhea. We examined antibody titers for viruses causing upper airway infectious diseases and identified antibodies for enteroviruses such as Echo 22, Entero 71, and Coxsackie B4. Our results suggested that TH might be caused by an infection of the enterovirus group.  相似文献   
976.
In the Late Triassic, an extremely large carbonate platform system (Dachstein-type platforms) developed on the margin of the Neotethys. On the wide inner platform cyclic peritidal, lagoonal successions were deposited. In the Transdanubian Range (Hungary), the lower part of the 1.5–2-km-thick cyclic succession (Upper Tuvalian–mid-Norian) is pervasively dolomitised, the upper part (Upper Norian–Rhaetian) is non-dolomitised; there is a transitional interval between them made up of partially dolomitised cycles. The peritidal–lagoonal cycles are commonly bounded by well-developed disconformity surfaces reflecting subaerial erosion that punctuated the marine carbonate accumulation. Truncation of the cycles was preceded by pervasive cementation of the previously deposited cycle. In the early stage of the platform evolution, tidal flat dolomitisation under semi-arid conditions led to the consolidation of the previously deposited sediments. The truncation surfaces were commonly covered by dolocretes. During the more humid Late Norian–Rhaetian period, the early cementation was followed by karstification, accumulation of wind-blown dust and pedogenesis. Erosion during regularly recurring subaerial exposure that commonly reached the previously deposited subtidal beds suggests eustatic control of the cyclicity and supports the application of an allocyclic model, even if the Milankovitch signal is imperfect.  相似文献   
977.
A quick-freezing and deep-etching method in combination with replica immunoelectron microscopy was applied for examining localization of hyaluronic acid and fibronectin on the upper surface layer of rat mandibular condylar cartilage. Rat temporomandibular joints were dissected with articular disks in order to leave the articular cartilage surface intact. The disks were slightly cut with razor blades for exposing the condylar articular cartilage surface. They were quickly frozen with the isopentane-propane cryogen (–193°C) and prepared for freeze-fracturing and deep-etching replica membranes. They were additionally treated with 5% SDS and 0.5% collagenase to keep some antigens attached on the replica membranes. After such a treatment, a routine immunogold method was applied for clarifying the localization of hyaluronic acid and fibronectin in the upper surface layer. Small immunogold particles for hyaluronic acid were mainly localized around upper filamentous networks covered with amorphous materials, but large immunogold ones for fibronectin were localized on deep thicker fibrils. We have revealed the native architecture of the upper surface layer of mandibular condylar cartilage on the replica membranes and also three-dimensional localization of hyaluronic acid and fibronectin by the immunogold method.  相似文献   
978.
Early excavations at the Willendorf site complex in Austria yielded a femoral diaphysis collected between 1883 and 1887 and a mandibular symphysis discovered in 1908--1909. The femoral section, Willendorf 1, derives from the Willendorf I site and direct AMS (14)C dating (24,250+/-180 years B.P.) assigns it to layer 9. The Willendorf 2 mandibular piece was excavated from layer 9 of the Willendorf II site, which is AMS (14)C dated to 24,000--23,900 years B.P. The Willendorf 1 femoral piece is relatively small and exhibits a pronounced pilaster and linear aspera, moderately elevated relative cortical area, and a level of diaphyseal robusticity in the middle of the European earlier Upper Paleolithic human range of variation, assuming similar body proportions. The Willendorf 2 mandibular symphysis has an inferior lingual torus, a planum alveolare, and a mental trigone with indistinct lateral tubercles, a clear fossa mentalis and a midline basilar rounding. In these features it is close to the majority of European earlier Upper Paleolithic mandibles.  相似文献   
979.
The holotype of the prosauropod dinosaur Blikanasaurus cromptoni n. gen. and n. sp., a partial hindlimb, is described from the lower Elliot Formation (= Red Beds) (upper Carnian or lower Norian; Upper Triassic) of Herschel district, Transkei, South Africa. The new prosauropod family Blikanasauridae is characterized by a hindlimb that is extremely stocky, especially the metatarsus, with the distal tarsals medially situated. Blikanasaurus was an early experiment in the direction of heavily-built, quadrupedal saurischians, but it was not on the evolutionary line that gave rise to the Sauropoda.  相似文献   
980.
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