青少年滑雪运动员的训练

在训练青少年竞速滑雪运动员的工作中,我们的出发点是把耐力作为一种决定性的身体素质,而且首先要予见到能够促使耐力提高的各器官和各系统的发展情况。当然,耐力素质的提高取决于机体的有氧供能能力,心脏血管系统和呼吸系统的机能发展,以及运动器官的条件。这也     

Effects of two medicinal plants Psidium guajava L. （Myrtaceae） and Diospyros mespiliformis L. （Ebenaceae） leaf extracts on rat skeletal muscle cells in primary culture

Crude decoction, aqueous and ethanolic extracts of two medicinal plants （Psidiura guajava and Diospyros raespiliformis）, widely used in the central plateau of Burkina Faso to treat many diseases were evaluated for their antagonistic effects on caffeine induced calcium release from sarcoplasmic reticulum of rat skeletal muscle cells. These different extracts showed a decrease of caffeine induced calcium release in a dose dependent manner. Comparison of the results showed that Psidiura guajava leaf extracts are more active than extracts of Diospyros mespiliformis and that crude decoctions show better inhibitory activity. The observed results could explaine their use as antihypertensive and antidiarrhoeal agents in traditional medicine, by inhibiting intracellular calcium release.     

丁香花开

刚刚过去的那个四月,我回到我在那长大的农场探望我的父母。我在屋外漫步,沉浸在“家”的舒适感觉中——当时我真的很需要家的慰藉。我习惯了加利福尼亚州南部那阳光明媚的早晨,艾奥瓦州清展凛冽的空气使我的鼻子、耳朵和没戴手套的双手感到一阵阵冰冷的刺痛。     

The Better Beginnings, Better Futures project: findings from grade 3 to grade 9

Although comprehensive and ecological approaches to early childhood prevention are commonly advocated, there are few examples of long-term follow-up of such programs. In this monograph, we investigate the medium- and long-term effects of an ecological, community-based prevention project for primary school children and families living in three economically disadvantaged neighborhoods in Ontario, Canada. The Better Beginnings, Better Futures (BBBF) project is one of the most ambitious Canadian research projects on the long-term impacts of early childhood prevention programming to date. Bronfenbrenner's ecological model of human development informed program planning, implementation, and evaluation. Using a quasi-experimental design, the BBBF longitudinal research study involved 601 children and their families who participated in BBBF programs when children were between 4 and 8 years old and 358 children and their families from sociodemographically matched comparison communities. We collected extensive child, parent, family, and community outcome data when children were in Grade 3 (age 8–9), Grade 6 (age 11–12), and Grade 9 (age 14–15). The BBBF mandate was to develop programs that would positively impact all areas of child's development; our findings reflect this ecological approach. We found marked positive effects in social and school functioning domains in Grades 6 and 9 and evidence of fewer emotional and behavioral problems in school across the three grades. Parents from BBBF sites reported greater feelings of social support and more positive ratings of marital satisfaction and general family functioning, especially at the Grade 9 follow-up. Positive neighborhood-level effects were also evident. Economic analyses at Grade 9 showed BBBF participation was associated with government savings of $912 per child. These findings provide evidence that an affordable, ecological, community-based prevention program can promote long-term development of children living in disadvantaged neighborhoods and produce monetary benefits to government as soon as 7 years after program completion.     

吹小号的天鹅

路易斯是只雄天鹅,他生下来就是个哑巴(yǎb),发不出声音。路易斯长大后,喜欢(xǐhu n)上了一个天鹅小姐,可他却没办法告诉她。怎么办呢?路易斯到学校里去学会了写字。他把想说的话写在石板上给天鹅小姐看。可是,天鹅小姐根本不认识字,她拍拍翅膀(chìbǎn),飞走了。在路易斯想不出办法的时候,爸爸打破了城里乐器店的玻璃(bōli),叼(diāo)出了一把小号给路易斯。可小号毕竟没有付钱,算是偷的。这成了路易斯的一块心病。慢慢地,路易斯的小号吹得越来越好,成为了著名(zhùmín)的小号演奏(yǎn zòu)家。最终,路易斯用小号声赢得了天鹅小姐的…     

Characterization and separation of Cryptosporidium and Giardia cells using on-chip dielectrophoresis

Dielectrophoresis (DEP) has been shown to have significant potential for the characterization of cells and could become an efficient tool for rapid identification and assessment of microorganisms. The present work is focused on the trapping, characterization, and separation of two species of Cryptosporidium (C. parvum and C. muris) and Giardia lambia (G. lambia) using a microfluidic experimental setup. Cryptosporidium oocysts, which are 2-4 μm in size and nearly spherical in shape, are used for the preliminary stage of prototype development and testing. G. lambia cysts are 8–12 μm in size. In order to facilitate effective trapping, simulations were performed to study the effects of buffer conductivity and applied voltage on the flow and cell transport inside the DEP chip. Microscopic experiments were performed using the fabricated device and the real part of Clausius—Mossotti factor of the cells was estimated from critical voltages for particle trapping at the electrodes under steady fluid flow. The dielectric properties of the cell compartments (cytoplasm and membrane) were calculated based on a single shell model of the cells. The separation of C. muris and G. lambia is achieved successfully at a frequency of 10 MHz and a voltage of 3 Vpp (peak to peak voltage).     

A "dry and wet hybrid" lithography technique for multilevel replication templates: Applications to microfluidic neuron culture and two-phase global mixing

A broad range of microfluidic applications, ranging from cell culture to protein crystallization, requires multilevel devices with different heights and feature sizes (from micrometers to millimeters). While state-of-the-art direct-writing techniques have been developed for creating complex three-dimensional shapes, replication molding from a multilevel template is still the preferred method for fast prototyping of microfluidic devices in the laboratory. Here, we report on a "dry and wet hybrid" technique to fabricate multilevel replication molds by combining SU-8 lithography with a dry film resist (Ordyl). We show that the two lithography protocols are chemically compatible with each other. Finally, we demonstrate the hybrid technique in two different microfluidic applications: (1) a neuron culture device with compartmentalization of different elements of a neuron and (2) a two-phase (gas-liquid) global micromixer for fast mixing of a small amount of a viscous liquid into a larger volume of a less viscous liquid.     

爸爸的新鞋

亲人的爱就像空气,也许你不曾注意,可是却一直围绕在你身旁。去关怀爱你的人吧,只要一点点,就能温暖他们很久很久……     

传播研究的历史取向--谈谈传播史的研究方法北大核心CSSCI

罗伯特·达恩顿（Robert Darnton）最近指出,“传播系统的历史久远,却鲜少获得历史研究者的青睐”（Darnton,1990：xvii）。这一观点倒是呼应了伊利莎白·爱森斯坦（Elizabeth Eisenstein）十年前的不满,即历史学家虽然断定印刷出版业力量强大,     

滑雪运动员肌肉力量的发展水平及关节的灵活性

大量的医学——生物学研究材料涉及运动训练对人机体的良好作用。在很多科研论文里包括不同专项的运动员局部肌肉力量的测量和关节活动的范围,用来反映机体的形态和机能状态。但是关于滑雪运动员这方面的材料是不详尽的。这些材料只是证实了滑雪运动员身材的特点,肌肉群力量的指标、关节活动的范围以及相对肌肉力量和专项耐力之间的正相关联系。滑雪运动员各个肌肉群的力量及大关节活动范围的研究应该是训练计划的一部分,而内容丰富的滑雪运动员的训练计划必须是因人而异的。为了说明这个问题,我们研究了39个