Differences in trunk and thigh muscle strength,endurance and thickness between elite sailors and non-sailors

Dinghy sailors lean their upper body over the windward side of the boat (‘hiking’) to keep the boat’s balance and maximise its speed. Sustaining the hiking position is essential for competitive performance and this study examined sport-specific differences of muscles relevant for hiking in elite sailors. Knee extensor muscle strength as well as trunk muscle strength, muscle endurance and muscle thickness were assessed in elite dinghy sailors (n = 15) and compared to matched, non-sailing controls (n = 15). Isometric extensor strength was significantly higher in sailors at 60° (+14%) but not at 20° knee flexion. Sailors showed significantly higher trunk flexor (but not extensor) strength under isometric (+18%) and eccentric (+11%) conditions, which was associated to greater muscle thickness (rectus abdominis +40%; external oblique +26%) and higher endurance for ventral (+66%) and lateral (+61%) muscle chains compared to non-sailors. Greater muscles thickness and the particular biomechanical requirements to maintain the hiking position may drive the increases in isometric and eccentric muscle strength as well as ventral and lateral trunk endurance. The current findings identified sport-specific muscle function differences and provide performance benchmarks for muscle strength and endurance in elite sailors.     

Sex-Related Responses to Eccentric-Only Resistance Training in Knee-Extensors Muscle Strength and Architecture

Purpose: The present study aimed to investigate whether or not eccentric-only training induced different sex-related adaptations in vastus lateralis muscle architecture and knee extensors strength. Methods: Thirteen healthy women and 13 healthy men were recruited. Vastus lateralis pennation angle, fascicle length, and muscle thickness, as well as knee extensors eccentric, isometric, and concentric peak torque and one-repetition maximum (1RM) were measured. Both women and men underwent a unilateral iso-load knee-extension eccentric-only training with 120% of the concentric 1RM, consisting of 4 sets × 10 repetitions twice a week for a total of 8 weeks. Results: Pennation angle increased in women (+ 14%, 95% CI [10, 17], effect size [ES] = 1.54) but not in men (+ 5%, 95% CI [?1, 11], ES = 0.28), while fascicle length increased in both women (+ 7%, 95% CI [4, 10], ES = 1.02) and men (+ 12%, 95% CI [8, 16], ES = 1.82) and muscle thickness increased in women (+ 13%, 95% CI [8, 18], ES = 1.11) and men (+ 11%, 95% CI [7, 15], ES = 0.89). In both women and men, eccentric (18%, 95% CI [11, 25], ES = 0.96, and 16%, 95% CI [9, 22], ES = 0.82, respectively), isometric (17%, 95% CI [11, 23], ES = 0.53, and 17%, 95% CI [10, 24], ES = 0.62), concentric (12%, 95% CI [7, 16], ES = 0.49, and 9%, 95% CI [5, 13], ES = 0.42) peak torque and 1RM (10%, 95% CI [6, 14], ES = 0.53, and 10%, 95% CI [5, 15], ES = 0.50) similarly increased after the intervention. Conclusions: This study showed that the adaptations in strength are not sex-dependent, but the increases in pennation angle only in women suggest that the changes in muscle architecture may depend on sex.     

导电聚苯胺薄膜的电磁学性能及其屏蔽特性

利用四探针测试法分析了导电聚苯胺(PANI-CSA)薄膜的电导率及其屏蔽特性,发现随着薄膜的厚度从4～40μm变化,导电聚苯胺薄膜的室温电导率在12～25S/cm范围内变化.并测试和分析了导电聚苯胺薄膜的屏蔽特性与薄膜厚度的关系,得到了导电聚合物PANI-CSA薄膜的电磁屏蔽效能在一定厚度范围内与理论值是一致的结论.     

钢筋混凝土保护层厚度及其施工方法

钢筋混凝土保护层在混凝土结构中起着重要的作用,但施工中往往被忽视。通过分析钢筋保护层在混凝土结构中的作用以及国家标准对保护层厚度的规定和施工中存在的问题,提出控制钢筋保护层厚度的有效措施,从而提高对钢筋保护层的认识。     

车辆集中荷载作用下脱空CRCP板的挠度与应力

基于挠度与应力等效原则,将作用于连续配筋混凝土路面(CRCP)中央的车辆集中荷载通过傅里叶级数展开为等效的半波正弦荷载.在荷载转换和小挠度弹性薄板理论的基础上,提出了车辆集中荷载作用下脱空地基上CRCP的挠度和应力计算公式,分析了参数的敏感性.结果表明:板的最大挠度与车辆集中荷载、板的宽度成正比,与板的横向弯曲刚度、板...     

尹世明《后土集》：厚实严谨 清新凝练

《尹世明诗文选第二卷·后土集》文字精练,文风清新,厚实严谨,精深耐读,朴实亲切,展现了尹世明教授多年来多方面的学术成就和工作成果,以及令人肃然起敬、积极进取的入世精神。     

鄂尔多斯盆地地表剥蚀厚度恢复综述

对适用于鄂尔多斯：盆地的各种剥蚀厚度的恢复方法进行综合分析,来恢复鄂尔多斯盆地地表剥蚀厚度．综合比较得出,运用镜质体反射率法,同时结合泥岩压实趋势外推法和地层对比法是目前恢复鄂尔多斯盆地地表剥蚀厚度较科学较准确的方法．     

辽东湾海冰资源量的遥感估算方法研究

该文提出了一种简单易行的海冰资源量遥感估算方法,包括提取海冰的结冰范围和反演冰厚分布。根据这种方法,利用2000年1月30日辽东湾NOAA/AVHRR资料,进行了海冰资源量遥感估算的尝试,得到了当天的海冰厚度分布图和海冰资源总量的数据,进而讨论了估算结果的合理性。研究得出的主要结论是：（1）NOAA/AVHRR资料的第一通道数据可以用于进行海陆分离和冰水分离;（2）基于反照率与海冰厚度指数关系的冰厚反演公式,可以用于海冰厚度的遥感估算;（3）得到的海冰资源量遥感估算结果,基本上符合辽东湾海冰分布的实际情况,可以为海冰资源的开发利用提供。     

通心络对颈动脉粥样硬化临床干预的对照研究

目的探讨通心络是否对颈动脉粥样硬化的发展有抑制作用。方法60例诊断"脑供血不足"的门诊病人,经Hpsonos5500型超声仪,证实颈动脉内膜有硬化改变或硬化斑块,随机进入通心络治疗或对照组。治疗组投给通心络胶囊4粒,3/d,对照组投给阿司匹林75mg/d、舒降之20mg/d,均连服180天。试验前后测定血清氧化低密度脂蛋白(OX-LDL)、单核细胞趋化因子(MCP-1)水平的变化,彩超检查颈动脉粥样硬化情况,观察内-中膜厚度(IMT)、内皮表面情况及硬化斑的变化。结果1.服药半年后两组血浆OX-LDL及MCP-1含量均显著下降(P<0.001)2.两组用药前血浆OX-LDL及MCP-1水平相当,无显著性差异(P>0.05)。治疗180天后,两组水平均明显下降,但对照组下降程度较试验组更明显,组间差异具有显著性(P<0.001)3.彩超示对照组血管IMT有所增加,试验组IMT有轻微增加,但无显著性差异(P>0.05)。结论两组干预对颈动脉粥样硬化的发展均有一定影响,其作用程度相近。病人对通心络胶囊的耐受良好,有高度依从性。     

不同成熟度及不同处理方式对百香果种子萌发特性的影响

通过研究成熟度、GA3、覆土厚度、温度和基质等条件对百香果种子萌发的影响,探讨其萌发特性。结果表明,生理成熟期的百香果种子发芽率最高;生理成熟期和近商品成熟期的种子先浸泡GA3溶液再播种会降低发芽率,而商品成熟期的种子经GA3溶液处理后可提高发芽率:覆土厚度控制在2.0 cm左右时发芽率和种苗成活率最高,发芽畸形率最低:种子在40℃环境下发芽率最高、发芽速度最快;基质以白水苔泥炭:珍珠岩为4:1的配制最适宜百香果种子发芽,可得到较高的发芽率和最低的发芽畸形率。研究结果为百香果高效高产栽培提供了科学依据和技术支持.