意大利蜜蜂(Apis mellifera L.)飞翔肌的发育     

叶巧真  卢爱平  张景强 《中山大学学报论丛》1995,(2)

全变态昆虫肌肉的转化与脊椎动物肌肉损伤修复有很大的相似之处。本文以意大利蜜蜂飞翔肌的发育阐明这一观点。两者的相似性表现为:①参与肌肉修复和成蜂飞翔肌形成的成肌细胞来源于胚细胞;②飞翔肌的发育过程中肌肉的转化和肌肉损伤修复均有幼虫残余肌丝或损伤部位残余肌丝和成肌细胞融合,成肌细胞与成肌细胞之间的融合等现象。这些结果为全变态昆虫肌肉的转化作为了解脊椎动物肌肉再生知识的便利模型的可行性,提供了理论依据。  相似文献   

Modeling Strain Rate Effect for Heterogeneous Brittle Materials     

MA Guowei  DONG Aiai  LI Jianchun 《天津大学学报(英文版)》2006,12(Z1)

Rocks are heterogeneous from the point of microstructure which is of significance to their dynamic failure behavior. Both the compressive and tensile strength of rock-like materials is regarded different from the static strength. The present study adopts smoothed particle hydrodynamics (SPH) which is a virtual particle based meshfree method to investigate strain rate effect for heterogeneous brittle materials. The SPH method is capable of simulating rock fracture, free of the mesh constraint of the traditional FEM and FDM models. A pressure dependent J-H constitutive model involving heterogeneity is employed in the numerical modeling. The results show the compressive strength increases with the increase of strain rate as well as the tensile strength, which is important to the engineering design.  相似文献   

再生混凝土力学性能的研究   总被引：1，自引：0，他引：1  

徐立民  蒋业浩  吴瑾 《连云港职业技术学院学报》2005,18(2):71-75

对再生混凝土力学性能的研究进行了综述，主要包括再生混凝土力学性能的抗压强度、弹性模量、干缩与徐变。研究表明，和普通混凝土相比，再生混凝土力学性能的抗压强度低，弹性模量小，干缩与徐变较大。最后提出了再生混凝土力学性能需要进一步研究的问题。  相似文献   

不同的吃喝玩乐     

宗明 《今日中学生》2007,(11):24

一、吃和喝吃苹果 eat an apple, 吃药 take medicine,吃糖 have some sweets,吃饭 have one's meals,吃馆子 dine out,吃惊 be surprised/  相似文献   

试论歌唱训练中的"松"与"紧"     

贺洁琼 《怀化学院学报》2011,30(6):110-111

放松是掌握歌唱基础的前提,一切声音技巧、情感表达都建立在放松的基础上.一副僵硬的喉咙不可能唱出优美自然的声音.旨在分析歌唱中哪些部分应该是松弛的,哪些部分该是使劲的,应该如何做才能达到一个收放自如的歌唱状态.着重从歌唱腔体,歌唱肢体,歌唱心理因素等三方面来进行研究和分析.  相似文献   

Rapid phenotypic evolution with shallow genomic differentiation during early stages of high elevation adaptation in Eurasian Tree Sparrows     

Yanhua Qu  Chunhai Chen  Ying Xiong  Huishang She  Yong E Zhang  Yalin Cheng  Shane DuBay  Dongming Li  Per G P Ericson  Yan Hao  Hongyuan Wang  Hongfeng Zhao  Gang Song  Hailin Zhang  Ting Yang  Chi Zhang  Liping Liang  Tianyu Wu  Jinyang Zhao  Qiang Gao  Weiwei Zhai  Fumin Lei 《国家科学评论(英文版)》2020,7(1):113

Known as the ‘third polar region’, the Qinghai-Tibet Plateau represents one of the harshest highland environments in the world and yet a number of organisms thrive there. Previous studies of birds, animals and humans have focused on well-differentiated populations in later stages of phenotypic divergence. The adaptive processes during the initial phase of highland adaptation remain poorly understood. We studied a human commensal, the Eurasian Tree Sparrow, which has followed human agriculture to the Qinghai-Tibet Plateau. Despite strong phenotypic differentiation at multiple levels, in particular in muscle-related phenotypes, highland and lowland populations show shallow genomic divergence and the colonization event occurred within the past few thousand years. In a one-month acclimation experiment investigating phenotypic plasticity, we exposed adult lowland tree sparrows to a hypoxic environment and did not observe muscle changes. Through population genetic analyses, we identified a signature of polygenic adaptation, whereby shifts in allele frequencies are spread across multiple loci, many of which are associated with muscle-related processes. Our results reveal a case of positive selection in which polygenic adaptation appears to drive rapid phenotypic evolution, shedding light on early stages of adaptive evolution to a novel environment.  相似文献   

Is there really an eccentric action of the hamstrings during the swing phase of high-speed running? part I: A critical review of the literature     

Bas Van Hooren  Frans Bosch 《Journal of sports sciences》2017,35(23):2313-2321

It is widely assumed that there is an eccentric hamstring muscle fibre action during the swing phase of high-speed running. However, animal and modelling studies in humans show that the increasing distance between musculotendinous attachment points during forward swing is primarily due to passive lengthening associated with the take-up of muscle slack. Later in the swing phase, the contractile element (CE) maintains a near isometric action while the series elastic (tendinous) element first stretches as the knee extends, and then recoils causing the swing leg to forcefully retract prior to ground contact. Although modelling studies showed some active lengthening of the contractile (muscular) element during the mid-swing phase of high-speed running, we argue that the increasing distance between the attachment points should not be interpreted as an eccentric action of the CE due to the effects of muscle slack. Therefore, there may actually be no significant eccentric, but rather predominantly an isometric action of the hamstrings CE during the swing phase of high-speed running when the attachment points of the hamstrings are moving apart. Based on this, we propose that isometric rather than eccentric exercises are a more specific way of conditioning the hamstrings for high-speed running.  相似文献   

The dynamic control ratio at the equilibrium point (DCRe): introducing relative and absolute reliability scores     

Tobias Alt  Axel J. Knicker  Heiko K. Strüder 《Journal of sports sciences》2017,35(7):688-693

Analytical methods to assess thigh muscle balance need to provide reliable data to allow meaningful interpretation. However, reproducibility of the dynamic control ratio at the equilibrium point has not been evaluated yet. Therefore, the aim of this study was to compare relative and absolute reliability indices of its angle and moment values with conventional and functional hamstring–quadriceps ratios. Furthermore, effects of familiarisation and angular velocity on reproducibility were analysed. A number of 33 male volunteers participated in 3 identical test sessions. Peak moments (PMs) were determined unilaterally during maximum concentric and eccentric knee flexion (prone) and extension (supine position) at 0.53, 1.57 and 2.62 rad · s^–1. A repeated measure, ANOVA, confirmed systematic bias. Intra-class correlation coefficients and standard errors of measurement indicated relative and absolute reliability. Correlation coefficients were averaged over respective factors and tested for significant differences. All balance scores showed comparable low-to-moderate relative (<0.8–0.9) and good absolute reliability (<10%). Relative reproducibility of dynamic control equilibrium parameters augmented with increasing angular velocity, but not with familiarisation. At 2.62 rad · s^–1, high (moment: 0.906) to moderate (angle: 0.833) relative reliability scores with accordingly high absolute indices (4.9% and 6.4%) became apparent. Thus, the dynamic control equilibrium is an equivalent method for the reliable assessment of thigh muscle balance.  相似文献   

负重训练和补充大豆多肽干预大鼠骨骼肌衰老过程的实验研究     

刘丰彬  赵斌  闫万军  马炳存 《天津体育学院学报》2010,25(1):33-37

目的:探讨负重训练和补充大豆多肽干预大鼠骨骼肌衰老过程的作用效果.方法:56只雄性SD大鼠随机分为7组:成年组,模型组,D-半乳糖小负重组,D-半乳糖大负重组,D-半乳糖补肽组,D-半乳糖补肽小负重组,D-半乳糖补肽大负重组.6周后处死大鼠,制作冰冻切片,测试血清以及骨骼肌各项指标.结果:与成年组相比,模型组大鼠体重和每日摄食量分别呈现升高和下降的趋势,负重和补肽可以在一定程度上缓解两种趋势,但都无统计学意义;模型组大鼠骨骼肌细胞出现萎缩和退行性改变等衰老的迹象,负重和补肽可以在一定程度上减轻这种现象;模型组大鼠血清SOD、SOD/MDA比值和骨骼肌总蛋白含量显著低于成年组,血清MDA显著高于成年组,运动和营养干预各组显著逆转这种趋势,并有明显的交互作用;与成年组相比,模型组大鼠骨骼肌脂褐素含量显著升高,负重或补肽可以一定程度上缓解或逆转这种趋势,两种具有明显的交互作用.结论:负重训练或补充大豆多肽均可以有效的预防大鼠骨骼肌衰老过早的出现,两种方式联合运用效果更为明显.  相似文献   

投掷运动员体成分的调查分析   总被引：1，自引：0，他引：1  

吕新颖 《北京体育大学学报》1999,(3)

通过对受试者体成分皮褶厚度的测定,并对其派生指标的比较发现：投掷选手皮脂较厚,其中重器械投掷选手达到肥胖标准。分析认为,这是由于其肌肉体积逐渐增大的同时,总伴随着皮下脂肪逐渐堆积的结果。肥胖不仅影响运动的效果,对身体健康也不利。建议投掷选手在促使肌肉体积增大的同时应积极采取消除脂肪的措施。  相似文献