吓坏水手的“幽灵”海域

<正>近日,在《环球科学》的一篇文章中,科学家揭开了一个古老的谜团——海洋中恢宏而短暂的“幽灵之光”究竟来自何处。一起去看看吧！1864年1月30日,阿拉巴马号的船长塞姆斯突然发现,自己正驶向一片不可思议的海域。“晚上8点左右,没有月亮,但天空晴朗,群星闪耀。我们航行的那片深蓝色的海域,突然变成了一片令人惊惧的雪白,好像有一种柔和的光,或者说是光晕照亮了那片海。但抬头看去,头顶的天空却只有一片死寂的漆黑。”塞姆斯在回忆录中写道。起初,     

Fingertip force and electromyography of finger flexor muscles during a prolonged intermittent exercise in elite climbers and sedentary individuals

The aim of this study was to characterize forearm muscle fatigue identified by the decrease in electromyogram median frequency and/or fingertip force during intermittent exercise. Nine elite climbers (international competitive level, USA 5.14a on sight) and ten non-climbers were instructed to maintain a fingertip force of 80% of their maximal voluntary contraction force on a dynamometer mimicking a rock climbing grip during a 5 s effort/5 s rest cycle for 36 repetitions (i.e. 6 min of exercise). Elite climbers lasted twice as long as non-climbers (climbers: 3 min; non-climbers: 1 min 30 s) before the force could no longer be maintained (i.e. the failure point). After this moment, fingertip force decreased and stabilized until the end of the exercise around 50% maximum voluntary contraction force in non-climbers and 63% in elite climbers. Electromyogram median frequency showed a greater decrease in non-climbers than in elite climbers before the failure point. No change in median frequency was observed after the failure point in elite climbers or in non-climbers. These results confirm that elite climbers are better adapted than non-climbers for performing the intermittent fingertip effort before the failure point. After this point, the better fingertip force of elite climbers suggests different forearm muscle properties, while the electromyography results do not provide any indication about the fatigue process.     

Effects of AM3 (Inmunoferon) on increased serum concentrations of interleukin-6 and tumour necrosis factor receptors I and II in cyclists

The aims of this study were to examine the changes in plasma concentrations of inflammatory cytokines induced by training and competition in professional cyclists. We report the serum concentrations of interleukin-6 (IL-6), tumour necrosis factor alpha (TNF-a), tumour necrosis factor receptors I and II (TNFR-I and -II) in a prospective, randomized, double-blind trial involving the administration of AM3 (Inmunoferon), an oral booster immunomodulator, or placebo to 16 professional cyclists (n = 8 in each group) for 65 consecutive days. Serum was collected just before treatment began (baseline), at the end of pre-competition training, before the mountain stage of the competition (60 days), 4 h after finishing this stage (62 days), and 18 h after the fifth and last day of competition (65 days). To determine the normal levels of cytokines and soluble TNF receptors, individual samples from 14 moderately trained healthy controls were studied. After 60 days of training, the serum concentrations of IL-6 did not differ significantly from those at the beginning of the study for either group of cyclists (placebo and AM3). A significant rise was seen in IL-6 concentrations in both the AM3 and placebo groups at 62 days, 4 h after finishing the mountain stage. The increase was significantly greater in the placebo group than in the AM3 group. At 65 days of treatment, 18 h after the fifth and last day of competition, IL-6 concentrations were similar to those recorded at the end of the training, but were significantly higher in the placebo group than in the AM3 group. At the end of training, serum TNFR-I concentrations in both groups of cyclists were significantly lower than at baseline. The concentrations of serum TNFR-I and -II both 4 h after finishing the mountain stage and 18 h after the fifth and last day of competition were significantly higher than those recorded after training in both groups. Professional cycling competition is associated with increases in serum IL-6 and TNFR-I and -II concentrations. Inmunoferon treatment reduced significantly the concentrations of IL-6 but not those of TNFR-I and -II.     

The angiogenetic effect of intramuscular administration of b-FGF and a-FGF on cardiac muscle: the influence of exercise on muscle angiogenesis

Although angiogenetic therapy using recombinant growth factors holds much hope for the treatment of ischaemic diseases, there are still many unanswered questions, including the method of administration, the correct dose of these factors, and the duration of the therapeutic approach. Exercise has also been suggested to induce neovascularizaiton in muscles. We evaluated the angiogenetic effects of the intramuscular administration of basic-fibroblast growth factor (b-FGF) and acidic-fibroblast growth factor (a-FGF) in rat heart, compared with rats who exercised daily. In conclusion, both the intramuscular administration of b-FGF and exercise increased significantly angiogenesis in the heart in contrast to the intramuscular administration of a-FGF, which was ineffective.     

滑翔机是怎样飞行的?

滑翔运动是最引人入胜的一种航空体育运动,也是青年们的一种体育运动。在一种没有发动机的叫做滑翔机的飞行器上面,人们可以在空中保持停留好几小时,航行数百公里的距离,不但能升得相当高,而且还能作一些优等航空术的特技表演。滑翔的这种锻炼能使人们熟悉飞行,培养出飞行人员的果断品质。许多苏联杰出的飞行员,例如,A.N.巴克雷斯金,A.N.莫洛得奇依等人,都是从滑翔飞行中锻     

石头是怎样生成的?

本文是从苏联伟大的矿物学家、通俗科学读物作家、科学院院士费尔斯曼(1883—1945)所著的“趣味矿物学”书中翻译过来的。“趣味矿物学”于1945年出版,已经有几国文字的翻译,是一本生动、活泼的通俗科学著作。我们已约请北京地质学院小塔同志负责翻译,以后将选出一部分陆续在本刊发表。原文文笔富有文艺性,在翻译上不易保持原来风格。有些地方为了使读者易于清楚明白起见,编者曾略加修改;如有错误,应由编者负责。     

生命的起源

科学家进行发掘工作以后,在地下发现了古代动物和植物的残骸(化石)。从这些卤获物可以确定一点,就是在远古时期,生物的种类没有现在这么繁多,结构也没有现在这么复杂。高级的动物和植物是由比较不复杂的有机体演发而成的。但是,最简单的有机体,即地球上一切生     

“诗魔”洛夫佳话

"雾正升起,我们在茫然中勒马四顾/手掌开始生汗/望远镜中扩大数十倍的乡愁/乱如风中的散发/当距离调整到令人心跳的程度/一座远山迎面飞来/把我撞成了/严重的内伤"这是著名诗人洛夫作于1979年《边界望乡》一诗中的一节,是他郁     

金庸和他的“修订工程”

金秋时节,金庸偕夫人查林乐怡出现在浙江海宁金庸小说国际学术研讨会上,这是金庸自1992年以来第五次回故乡。他的故乡情,他的求学记,     

七歲兒童的特點

兒童到了七歲年齡,在生理和心理上已經具備實施有系統的學校教育所必需的基本條件。這些就是神經系統比較堅固,神經疲勞程度比較早幾年減少,由此使兒童可以省去午睡,還有就是注意能力比較過去更为耐久。七歲兒童所達到的智力發展程度,和所積累的相當多的經驗,已使他能有基本的邏輯來討論問題,能對許多不複雜的現象作分析和