Primate spinal interneurons show pre-movement instructed delay activity.

Preparatory changes in neural activity before the execution of a movement have been documented in tasks that involve an instructed delay period (an interval between a transient instruction cue and a subsequently triggered movement). Such preparatory activity occurs in many motor centres in the brain, including the primary motor cortex, premotor cortex, supplementary motor area and basal ganglia. Activity during the instructed delay period reflects movement planning, as it correlates with parameters of the cue and the subsequent movement (such as direction and extent), although it occurs well before muscle activity. How such delay-period activity shapes the ensuing motor action remains unknown. Here we show that spinal interneurons also exhibit early pre-movement delay activity that often differs from their responses during the subsequent muscle activity. This delay activity resembles the set-related activity found in various supraspinal areas, indicating that movement preparation may occur simultaneously over widely distributed regions, including spinal levels. Our results also suggest that two processes occur in the spinal circuitry during this delay period: the motor network is primed with rate changes in the same direction as subsequent movement-related activity; and a superimposed global inhibition suppresses the expression of this activity in muscles.     

几种灵长类毛发的亚显微结构比较研究

根据毛小皮形态、毛发髓部结构和色素颗粒分布等综合性特征,对几种代表性的灵长类动物(白眉长臂猿、猕猴、短尾猴、黑猩猩)和现代人的头发进行了亚显微结构的比较研究,发现现代人头发和其它灵长类毛发的亚显微结构存在明显不同的特点,而各科灵长类之间又有程度不同的差异,因此,它可以作为灵长类代表性种属鉴别有意义的参考依据。     

几种灵长类毛发的亚显微结构比较研究

根据毛小皮形态、毛发髓部结构和色素颗粒分布等综合性特征,对几种代表性的灵长类动物(白眉长臂猿、猕猴、短尾猴、黑猩猩)和现代人的头发进行了亚显微结构的比较研究,发现现代人头发和其它灵长类毛发的亚显微结构存在明显不同的特点,而各科灵长类之间又有程度不同的差异,因此,它可以作为灵长类代表性种属鉴别有意义的参考依据。     

Noggin and retinoic acid transform the identity of avian facial prominences.

The signals that determine body part identity in vertebrate embryos are largely unknown, with some exceptions such as those for teeth and digits. The vertebrate face is derived from small buds of tissue, facial prominences, that surround the embryonic oral cavity. In chicken embryos, the skeleton of the upper beak is derived from the frontonasal mass and maxillary prominences. Here we show that bone morphogenetic proteins (Bmps) and the vitamin A derivative, retinoic acid (RA), are used to specify the identity of the frontonasal mass and maxillary prominences. Implanting two beads adjacent to the stage-15 presumptive maxillary field, one soaked in the Bmp antagonist Noggin and one soaked in RA, induces a duplicate set of frontonasal mass skeletal elements in place of maxillary bones. We also show that the duplicated beak is due to transformation of the maxillary prominence into a second frontonasal mass and not due to ectopic migration of cells or splitting of the normal frontonasal mass. Thus the levels of Bmp and RA determine whether specific regions of the face form maxillary or frontonasal mass derivatives.     

Primate eta-globin DNA sequences and man's place among the great apes

Molecular studies indicate that chimpanzee and gorilla are the closest relatives of man (refs 1-7 and refs therein). The small molecular distances found point to late ancestral separations, with the most recent being between chimpanzee and man, as judged by DNA hybridization. Kluge and Schwartz contest these conclusions: morphological characters group a chimpanzee-gorilla clade with the Asian ape orang-utan in Kluge's cladistic study and with an orang-utan-human clade in Schwartz's study. Clearly, extensive sequencing of nuclear DNA is needed to resolve by cladistic analysis the branching order within Hominoidea. Towards this goal, we are sequencing orthologues of the primate psi eta-globin locus. Here, we compare the newly completed sequences of orang-utan and rhesus monkey with human, chimpanzee, gorilla, owl monkey, lemur and goat orthologues. Our findings substantially increase the evidence indicative of a human-chimpanzee-gorilla clade with ancestral separations around 8 to 6 Myr ago. We also verify that neutral hominoid DNA evolved at markedly retarded rates.     

导游词英语介词与汉语对译技巧

鉴于介词在英语及汉语中使用频率及发挥作用的不对称性,导游的讲解词要做到既能忠实于旅游资源的历史真实性,又必须考虑英语游客的审美心理.认识英汉语的这种差异,还要运用变译策略,在具体的翻译过程中把这些元素相结合,才能达到满足游客审美的交际需求.     

导游词英语介词与汉语对译技巧

鉴于介词在英语及汉语中使用频率及发挥作用的不对称性,导游的讲解词要做到既能忠实于旅游资源的历史真实性,又必须考虑英语游客的审美心理。认识英汉语的这种差异,还要运用变译策略,在具体的翻译过程中把这些元素相结合,才能达到满足游客审美的交际需求。     

面神经核神经纤维联系及功能

面神经核作为一个传统意义上的运动性神经核团,在咀嚼、吞咽、吸吮、表情和发音等方面发挥重要作用.近年来的研究表明,面神经核内除了有运动性神经元外,还有形态较小的非运动性神经元,它们可能参与机体呼吸等其他功能活动的调节.本文主要介绍面神经核的形态结构,纤维联系及功能,以便更深入、全面的认识面神经核.     

Summary of phylogeny in subfamily Colobinae (Primate: Cercopithecidae)

The phylogeny of the colobine monkeys has a complex evolutionary history,evolving several distinct radiations and owned a wide range of forest and woodland habits in tropical Africa and in southern and eastern Asia.Understanding the true evolutionary history of the colobine monkeys becomes an important field and has received special attention.In this article,we review phylogeny of Colobinae based on previous fossil,cytological,morphological and molecular evidence and indicate the phylogenetic controversies.This review is expected to guide the future research of Colobinae phylogeny,and also provide theoretic evidence for the conservation of these highly endangered and unique primates.     

脸部表情动画的实现

用计算机动画技术合成人的面部表情动画是人体动画研究的一个重点。本文分析了人脸的生理结构组成和脸部表情与表情单元形变之间的关系，研究了包括局部变形箱变形、线性局部变形和密度球收缩和舒张变形在内的三种面部肌肉变形方法，在此基础上，提出了一个基于复合多组局部变形操作的脸部表情动画的模拟算法。通过调相关整表情单元的形变因子一时间参数曲线，有效地控制了脸部表情的动画过程，从而实现了脸部表情动画。     

网络流问题的二个注释及有关算法的改进

鉴于网络理论在人力物力分配方面和物资调运方面等具有重大的应用意义,特对其中的网络流问题作出如下二个注释及有关算法的改进:1.最大流问题及有关算法的改进;2.最小费用的最大流问题及有关算法。     

网络流问题的二个注释及有关算法的改进

鉴于网络理论在人力物力分配方面和物资调运方面等具有重大的应用意义，特对其中的网络流问题作出如下二个注释及有关算法的改进：1．最大流问题及有关算法的改进；2．最小费用的最大流问题及有关算法。     

Geophysics. Longitudinal variation in springtime ozone trends

Satellite measurements indicate that mid-latitude ozone depletion in the Northern Hemisphere spring during 1979-97 was worst over Europe and Russia. Here we show that these longitudinal differences in ozone trends are due to a combination of decadal variations in the circulation and transport of ozone-depleted air from the polar vortex. Any increase in ozone depletion in the polar vortex as a result of future cooling of the stratosphere would therefore be particularly bad over Europe and Russia.