Altitude and wind effects on long jump performance with particular reference to the world record established by Bob Beamon

An analysis of long jump performance, including both the approach and aerial phases, is applied to Bob Beamon's legendary leap at the Mexico City Olympic Games of 1968. It is shown that the combined effects of altitude and wind assistance yielded an increment in the length of the jump of about 31 cm, compared to a corresponding jump at sea level under still air conditions. The main factor is shown to be the increased sprinting speed attained under favourable conditions of wind and altitude.     

与圈梁现浇在一起的天沟挑檐的抗倾覆设计

本通过理论分析和工程实例，对与圈梁现浇在一起的天沟桃檐的抗倾覆设计问题进行了探讨，阐明了天沟桃檐产生的抗倾覆力矩将由哪些因素来平衡，提出了抗扭支座的概念，形成了明确合理、概念清晰的设计理念。     

Attrition resistant catalyst for dimethyl ether synthesis in fluidized-bed reactor

Fluidized-bed reactor is a candidate for dimethyl ether （DME） synthesis from syngas because of its excellent heat removal capability. In order to improve the attrition resistance of catalyst, an amount of silica sol as binder was added to the catalyst composed of methanol synthesis component CuO/ZnO/Al2O3 and methanol dehydration component HZSM-5, which was prepared by coprecipitation and shaped by spray drying to get spherical particles. The effect of silica sol on the catalytic activity was investigated in a fixed-bed flow microreactor. Based on the experiment results, silica sol in the range of 0-20wt% had small effect on the catalytic activity. Generally, the CO conversion and DME yield decreased with the increase in concentration of silica sol, while the attrition resistance of catalysts increased with increasing silica sol, indicating that it was feasible to improve the attrition resistance without greatly sacrificing the activity of catalyst. In addition, the characterizations of catalysts were carried out using Brunauer-Emmett-Teller （BET）, X-ray powder diffraction （XRD） and temperature programmed reduction （TPR）.     

新课程实施中教师的改革与抗拒

参照美国"基于关心的变革采纳模式(CBAM)"的研究理论以及我国中小学教师的课程实施现状,可将教师实施新课程的水平大致分为机械实施、常规化、精致加工、整合、创新五个层次,而教师实施新课程的态势主要表现为夹杂着改革与抗拒成分的"激进主义、保守主义和中庸主义"三种倾向.新课程改革必须关注教师的态度与态势,才能促进教师与新课程同行.     

“七月诗派”抗战时期在桂林的诗歌创作

“七月诗派”作为一个在腥风血雨的严峻现实中崛起的高歌救亡的诗歌流派,这些诗人们在抗战炮声响起之后分别在根据地、敌后、国统区从事着民族的解放运动。由于当时桂林处于特殊的地理环境和政治地位,使得一部分“七月派”诗人先后驻足于桂林。他们在桂林的诗歌创作及活动,极大地繁荣了抗战时期的桂林诗坛,声援了全国的抗战斗争。     

死亡背景下的斯芬克斯之思——福柯人学思想初探

福柯对人的思考是在死亡的背景下展开的,他继尼采的“上帝死了”之后进一步提出了“人的死亡”这一具有多重含义的判断;并在一系列的著作中对造成“人的死亡”的外在社会原因也即权力的具体内容与规律进行了分析与阐述;最后指出在权力的支配下,人的复活只能依靠随时随地的反抗。     

从“西西弗”到“普罗米修斯”——个人反抗与群体反抗

作为“苦难与阳光之子”的加缪,在自身的创作中体现出独特的反抗精神,爱与信仰是其反抗精神的实质。在他的哲学随笔《西西带神话》和《反抗者》中,希腊神话人物“西西弗”与“普罗米修斯”是独具特色的反抗者形象,他们分剐为“个人反抗的代表”和“群体反抗的代表”,二者能够以独特的角度折射和再现出加缪的反抗精神。     

抗生素耐药性的来源与控制对策

抗生素除了大量用于人类疾病的治疗外,还作为饲料添加剂被广泛应用于动物养殖业。微生物的抗生素耐药性就是指微生物能够在抗生素存在的情况下生长和繁殖。抗生素耐药性是环境微生物固有的,即所谓的内在抗性,但是人类大量使用抗生素带来的抗生素抗性基因的扩散和传播普遍存在,且已开始威胁到全球人群的健康。微生物对抗生素的抗性主要有3个机制:(1)抗生素的外排;(2)抗生素的降解或修饰;(3)抗生素作用位点的保护。大量研究表明,抗生素的使用和抗生素抗性的蔓延呈现良好的相关性,而且环境微生物的抗性可以通过基因横向转移向人类致病菌扩散,最终可能导致超级细菌的爆发,直接影响人类健康。为了应对全球性的抗生素抗性问题,必须加强:(1)全球抗生素使用和环境排放的监管政策和管理体系;(2)建立快速和透明的抗生素耐药性监测体系,使其涵盖医院、养殖业、污水处理厂等;(3)建立抗生素药物创新基金,通过政府和企业的联合,加快新型药物的研制;同时加强知识产权保护,使新药创制走上可持续之路;(4)加强抗生素耐药性相关的基础与应用研究,包括耐药性发生和传播的生态学机制,消除和缓解耐药性发生和传播的环境技术及其系统解决方案等,包括改进污水处理厂的处理工艺,削减出水中抗性基因和抗性菌的比例;(5)加强抗生素耐药性的科普宣传,提高全社会对耐药性的认知能力,从而在源头上有效控制抗生素在农业和医疗方面的滥用及其环境污染。     

The effect of periodized resistance training on accelerative sprint performance

The purpose of this study was to assess the effect of periodized resistance training on accelerative sprint performance. Sixteen physically active men participated in a randomized controlled study. An experimental group (n = 10) completed an 8-week periodized resistance training intervention, while a control group (n = 6) did not train. Pre- and post-training measures of 20-m straight-line sprint time, including a 10-m split, maximum strength, and explosive strength, were recorded. Flight time, stance time, stride length, and stride frequency were quantified from digitized video recordings of the first three strides of the 20-m sprint. Resistance training resulted in significant increases in maximum strength (parallel back squat: 19%) and explosive strength (6–10%). However, both groups increased 0–10 m sprint times (experimental group = 6%; control group = 3%) while 10–20 m times were reduced (experimental group = 7%; control group = 4%), highlighting the mechanical differences between the distinct sprint phases. The change during the 0–10 m interval was accompanied by a reduction in stride frequency during the first three strides. Strength coaches should be aware that the potential benefits of increased muscular strength during short sprints are likely to be affected by mechanical specificity and that improvements in sprinting performance may not occur immediately after a period of resistance training.     

A comparison of muscle activity and 1-RM strength of three chest-press exercises with different stability requirements

Abstract

The purpose of this study was to compare one-repetition maximum (1-RM) and muscle activity in three chest-press exercises with different stability requirements (Smith machine, barbell, and dumbbells). Twelve healthy, resistance-trained males (age 22.7 ± 1.7 years, body mass 78.6 ± 7.6 kg, stature 1.80 ± 0.06 m) were tested for 1-RM of the three chest-press exercises in counterbalanced order with 3–5 days of rest between the exercises. One-repetition maximum and electromyographic activity of the pectoralis major, deltoid anterior, biceps, and triceps brachii were recorded in the exercises. The dumbbell load was 14% less than that for the Smith machine (P ≤ 0.001, effect size [ES] = 1.05) and 17% less than that for the barbell (P ≤ 0.001, ES = 1.11). The barbell load was ～3% higher than that for the Smith machine (P = 0.016, ES = 0.18). Electrical activity in the pectoralis major and anterior deltoid did not differ during the lifts. Electrical activity in the biceps brachii increased with stability requirements (i.e. Smith machine <barbell <dumbbells; P ≤ 0.005; ES = 0.57, 1.46, and 2.00, respectively), while triceps brachii activity was reduced using dumbbells versus barbell (P = 0.007, ES = 0.73) and dumbbells versus Smith machine (P = 0.003, ES = 0.62). In conclusion, high stability requirements in the chest press (dumbbells) result in similar (pectoralis major and anterior deltoid), lower (triceps brachii) or higher (biceps brachii) muscle activity. These findings have implications for athletic training and rehabilitation.