The foot and ankle of Australopithecus sediba

A well-preserved and articulated partial foot and ankle of Australopithecus sediba, including an associated complete adult distal tibia, talus, and calcaneus, have been discovered at the Malapa site, South Africa, and reported in direct association with the female paratype Malapa Hominin 2. These fossils reveal a mosaic of primitive and derived features that are distinct from those seen in other hominins. The ankle (talocrural) joint is mostly humanlike in form and inferred function, and there is some evidence for a humanlike arch and Achilles tendon. However, Au. sediba is apelike in possessing a more gracile calcaneal body and a more robust medial malleolus than expected. These observations suggest, if present models of foot function are correct, that Au. sediba may have practiced a unique form of bipedalism and some degree of arboreality. Given the combination of features in the Au. sediba foot, as well as comparisons between Au. sediba and older hominins, homoplasy is implied in the acquisition of bipedal adaptations in the hominin foot.     

The endocast of MH1, Australopithecus sediba

The virtual endocast of MH1 (Australopithecus sediba), obtained from high-quality synchrotron scanning, reveals generally australopith-like convolutional patterns on the frontal lobes but also some foreshadowing of features of the human frontal lobes, such as posterior repositioning of the olfactory bulbs. Principal component analysis of orbitofrontal dimensions on australopith endocasts (MH1, Sts 5, and Sts 60) indicates that among these, MH1 orbitofrontal shape and organization align most closely with human endocasts. These results are consistent with gradual neural reorganization of the orbitofrontal region in the transition from Australopithecus to Homo, but given the small volume of the MH1 endocast, they are not consistent with gradual brain enlargement before the transition.     

Australopithecus sediba hand demonstrates mosaic evolution of locomotor and manipulative abilities

Hand bones from a single individual with a clear taxonomic affiliation are scarce in the hominin fossil record, which has hampered understanding the evolution of manipulative abilities in hominins. Here we describe and analyze a nearly complete wrist and hand of an adult female [Malapa Hominin 2 (MH2)] Australopithecus sediba from Malapa, South Africa (1.977 million years ago). The hand presents a suite of Australopithecus-like features, such as a strong flexor apparatus associated with arboreal locomotion, and Homo-like features, such as a long thumb and short fingers associated with precision gripping and possibly stone tool production. Comparisons to other fossil hominins suggest that there were at least two distinct hand morphotypes around the Plio-Pleistocene transition. The MH2 fossils suggest that Au. sediba may represent a basal condition associated with early stone tool use and production.     

Australopithecus sediba at 1.977 Ma and implications for the origins of the genus Homo

Newly exposed cave sediments at the Malapa site include a flowstone layer capping the sedimentary unit containing the Australopithecus sediba fossils. Uranium-lead dating of the flowstone, combined with paleomagnetic and stratigraphic analysis of the flowstone and underlying sediments, provides a tightly constrained date of 1.977 ± 0.002 million years ago (Ma) for these fossils. This refined dating suggests that Au. sediba from Malapa predates the earliest uncontested evidence for Homo in Africa.     

Australopithecus garhi: a new species of early hominid from Ethiopia

The lack of an adequate hominid fossil record in eastern Africa between 2 and 3 million years ago (Ma) has hampered investigations of early hominid phylogeny. Discovery of 2.5 Ma hominid cranial and dental remains from the Hata beds of Ethiopia's Middle Awash allows recognition of a new species of Australopithecus. This species is descended from Australopithecus afarensis and is a candidate ancestor for early Homo. Contemporary postcranial remains feature a derived humanlike humeral/femoral ratio and an apelike upper arm-to-lower arm ratio.     

Complete fourth metatarsal and arches in the foot of Australopithecus afarensis

The transition to full-time terrestrial bipedality is a hallmark of human evolution. A key correlate of human bipedalism is the development of longitudinal and transverse arches of the foot that provide a rigid propulsive lever and critical shock absorption during striding bipedal gait. Evidence for arches in the earliest well-known Australopithecus species, A. afarensis, has long been debated. A complete fourth metatarsal of A. afarensis was recently discovered at Hadar, Ethiopia. It exhibits torsion of the head relative to the base, a direct correlate of a transverse arch in humans. The orientation of the proximal and distal ends of the bone reflects a longitudinal arch. Further, the deep, flat base and tarsal facets imply that its midfoot had no ape-like midtarsal break. These features show that the A. afarensis foot was functionally like that of modern humans and support the hypothesis that this species was a committed terrestrial biped.     

Endocranial features of Australopithecus africanus revealed by 2- and 3-D computed tomography

The earliest hominid from South Africa, Australopithecus africanus, is known from only six specimens in which accurate assessment of endocranial capacity and cranial venous outflow pattern can be obtained. This places a severe limit on a number of hypotheses concerning early hominid evolution, particularly those involving brain-body size relationships and adaptations of the circulatory system to evolving upright posture. Advances in high-resolution two- and three-dimensional computed tomography (CT) now allow the inclusion of another important specimen to this list, MLD 37/38 from Makapansgat. A new computer imaging technique is described that "reconstructs" the missing portions of the endocranial cavity in order to determine endocranial capacity. In addition, CT evaluation allows assessment of cranial venous outflow pattern even in cases where the endocranial cavity is completely filled with stone matrix. Results show that endocranial capacity in this specimen is less than originally proposed and also support the view that gracile and robust australopithecines evolved different cranial venous outflow patterns in response to upright postures.     

A neural effect of partial visual deprivation in humans

Certain human subjects have considerable sensitivity differences in the visual resolution of vertical gratings as compared to horizontal gratings. Although only subjects with pronounced ocular astigmatism exhibit this effect, the differences are of neural, rather than optical, origin. It is argued that the resolution anisotropies result from early abnormal visual input caused by astigmatism. This abnormal input permanently modifies the brain.     

黑熊骨盆骨解剖特性的形态学观察

为丰富有关黑熊的形态学知识，以1头5岁雌性黑熊为研究对象，测量了黑熊骨盆骨的44项指标，并计算16项指数，将测量结果与大熊猫骨盆骨的15项指标进行比较，发现除髋臼间宽、耻骨长、荐髂联合长和骨盆联合长有较明显差异外，其余12项均无显著差异．     

中国牛肉市场模型构建与基础模拟

为了解我国牛肉市场现状及大致走向,本研究构建包括牛肉生产、进出口贸易、城乡居民消费、价格传递及市场出清在内的牛肉市场局部均衡模型,拟合各方程并对市场的未来发展状况进行预测。研究结果表明:农村居民牛肉消费对价格和收入水平的敏感度高于城镇居民,居民牛肉消费对收入敏感度更高;未来我国肉牛生产和市场规模将得到不断提升;农村居民及城乡户外的消费潜力巨大;牛肉价格和肉牛出栏价格将不断上涨;牛肉进口剧增而出口不断萎缩。至2020年,我国牛肉产量将达到723.17万t,净进口量为55.40万t,城乡居民总消费量为600.35万t;肉牛出栏价格和牛肉价格分别上升至37.11和79.50元/kg。     

延边黄牛骨盆骨形态学特征观察比较

以延边大学解剖教研室延边黄牛骨盆骨标本(3♂,3♀)为研究对象,应用常规解剖学方法对延边黄牛骨盆骨的40项指标进行测量,计算出14项测量指数.并将公牛和母牛的各项指标进行比较.发现公牛的骨盆入口中矢状径与骨盆入口横径比大于母牛,母牛的骨盆入口指数大于公牛,母牛的骨盆出口指数大于公牛.肉眼直接观察可见公牛的坐骨棘高度大于母牛.     

局部双层网壳结构的静力特性分析

对局部双层网壳分别采用完全刚节点、安全铰节点，单层处采用刚节点，双层处采用铰节点，单双层连接处杆件一端刚接一端铰接的3种计算模型，利用Anasys5.5程序对其静力特性进行分析，以便确定一种较为合理的结构形式，所得结果可为类似结构设计提供依据。     

局部双层网壳几何非线性分析

根据梁－柱单无非线性有限元理论，采用弧长法与修正Newton-Raphson法相结合的迭代法，编制了网壳结构几何非线性分析程序，对不同矢跨比下单层网壳和局部双层网壳的静力稳定性能进行分析比较。所得结果可为类似结构设计提供依据。