平底帆船的波浪干扰力初探

目的研究波浪对平底帆船的干扰力。方法以小型平底帆船为对象,基于线性切片理论计算一阶规则波浪对船体的干扰力,分析波浪干扰力对帆船运动的影响。结果计算了斜浪时波高对干扰力的影响;遭遇角对干扰力大小、振荡周期的影响;波浪频率对干扰力振荡周期的影响,及斜浪对船体横漂的影响等。结论帆船在波浪中行驶时,遭遇角是影响帆船运动状态的关键因素之一,为保持正确航向应适时修正遭遇角。     

利用容量型肺动脉导管监测心室压力-容量关系的研究与应用

20世纪70年代Swan和Ganz两人从港湾帆船漂流得到启示,发明了肺动脉漂浮导管(Swan-Ganz catheter),最初只能测肺动脉血压和采血样.通过中心静脉压(central venous pressure,CVP)了解右心前负荷;通过肺动脉楔压(pulmonary anery wedge pressure,PAWP)了解左心前负荷.随后利用温度稀释法实现了测量心排血量(cardiac output,CO).CO测定的出现给血流动力学监测带来了重大变革.很多数据都可以通过CO计算出来.     

南极医学研究的近况

人类正式向南极进军已有200多年历史,其间经历了上一世纪的驾驰帆船去探险的“帆船时代”,本世纪初利用狗拉雪橇深入南极大陆内地探险的“英雄时代”,本世纪50年代使用大量机械化装备进行科学考察的“机械化时代”,60年代建立永久性基地,利用最新科学技术执行大规模研究计划的“科学时代”(由于展开卓有成效的和平国际合作,故又称为“国际合作时代”),70年代由于资源问题突出,各国加紧对南极的资源调查,故正向“资源时代”转换。 我国南极事业于80年代初才开始起步,但发展很快,已成为人类和平利用南极伟大事业中的重要一员。随着人类第一次进入南极,就伴随着对医学的需求,当前,如何保障进入南极人员的身心健康和有效的科学活动,如何保护地球上唯一保持原始状态自然环境免遭人为破坏,又如何利用这种特殊洁净环境进行造福人类的生命科学研究,越来越引起人们的注意,本刊邀请从事或亲自参加南极考察的科学工作者撰写这一专题,由于资料来源困难,难免挂一漏万,目的是引起更多的关注,吸引更多有志者从事这方面的研究,为我国南极科学事业作出新的贡献。     

好心态造就好心情

心情,是相当宝贵的。“天的心情好了,天就晴朗了;水的心情好了,水就流淌了;花的心情好了,花就开放了;鸟的心情好了,鸟就飞翔了。打开心灵的天窗,让阳光漫步;做个阳光的人,把爱付出。你的心情好了,你就微笑了;我的心情好了,我就快乐了;他的心情好了,他就歌唱了;大家的心情好了,世界就祥和了”。     

都得装修

同事大马是结婚时买的房,如今大马的儿子都上初中了。当年英俊的大马也是人到中年,身子发了福,烟瘾一天比一天大,他的娇妻肤色也不如从前了,眼角还有了许多鱼尾纹。十多年过去了,大马的新房成了旧房,墙面上的乳胶漆脱落了不少,木地板也有许多开裂了。     

网瘾少年:和父母的“拉锯战”

近半年来,因为网络游戏问题,小刚的父母和儿子陷入了一场"拉锯战"之中为了帮助儿子戒除网络游戏成瘾问题,父母使出了所有的"招数",但最终还是输给了儿子母亲说,小刚当初是以不错的成绩进入现在这所区重点高中的。自从迷恋上了网络游戏,他的学习成绩就一路直线下滑,已经从入学时的班级前五滑落到了现在的班级倒数位。为了使小刚能停止玩网络游戏,他们的嘴皮都快要磨破了。跟他讲了很多道理,也想了很多办法劝他,但都没有什么效果。实在气急了,也打过他、骂过他,可小刚的网络游戏行为不仅没有任何收敛,相反更加着迷了每     

每一朵祝福的花儿都是芬芳的

表姐的女儿冉冉12岁生日时,正赶上学校放寒假,我就带着9岁的儿子去了表姐家。我们去时,她家里已经来了好多同学,兴许是放了寒假,孩子们的心情格外轻松愉快,唧唧喳喳的,好不热闹。冉冉的同学都送了礼物,她的书桌已堆满了,后来同学的礼物只好放在了她的小床上,很快,小床也占去了一半。     

离婚协议书写好之后

心理困扰他这究竟是为什么?落座心理咨询室,女士未曾开口泪先流。原来昨天和丈夫大吵一架,已经写好了离婚协议书。她今年五十多岁了,两个孩子都大了,女儿出嫁了,儿子也就要成家。本来,就要安享晚年生活的岁数了,没想到突然发现丈夫移情别恋,在外面有了女人。来访者心里充满了委屈,这么多年来为这个家付出了那么多,为他也付出了不少,可是到头来,他却闹出这样的事,跑到别的女人那里去了。     

“新退休族”:现在就退休?

厌倦了尔虞我诈的职场,厌倦了无休无止的竞争,厌倦了镜子里自己职业性的微笑……有一天,累了,你想到了"退休"。这个词似乎是父辈们的专利。然而,现代城市中,却     

医学数据挖掘综述

本文主要综述了有关数据挖掘的概念,综述了医学数据的一些特点,以及医学数据挖掘的关键问题,介绍了医学数据挖掘的主要应用方向,并给出了一些具体的应用实例.     

医院船船员自我效能感与人格特征、生活质量的关系

目的探讨医院船船员自我效能感与人格特征、生活质量的关系。方法对医院船122人采用自行设计一般项目调查表、艾森克个性测量问卷(EPQ)、一般自我效能感量表(GSES)和健康调查简表(SF-36)在出海前3天及航行第15天进行测评。结果晕船病的发生率为83.2%;航行中船员精神质和神经质因子分显著高于出海前(t=-3.69,-4.01;P0.01和P0.001);航行中船员的生理职能、总体健康、活力、情感职能、精神健康评分均显著低于出海前(t=3.02,5.73,5.02,6.44,5.06;P0.01和P0.001);按标准回归系数绝对值大小计算,影响自我效能感的因素由强到弱依次总体健康、活力、神经质、情感职能、生理职能(t=5.418,4.608,-3.523,3.618,3.019;P0.001和P0.01)。结论船员自我效能感高可以增强心理适应能力和缓解由航海应激造成的心理紧张,提高生活质量。     

Heat acclimation decreased oxidative DNA damage resulting from exposure to high heat in an occupational setting

Heat acclimation is a physiologically and biochemically adapted process when species transition from one environmental temperature to one of the increased temperature. There is very limited epidemiological evidence on the heat-related impacts during exposure to extremely high heat in an occupational environment. This study sought to identify a potential biomarker of heat acclimation and the burden of heat on the body. The aim of this study was to elucidate oxidative DNA damage and heat acclimation through a self-comparison study design in navy boiler tenders, subjects exposed to extremely high heat in an occupational setting. Fifty-eight male soldiers who work in a boiler room were recruited for this study. The subjects were initially assessed with a health examination and body composition assessment before sailing. In order to compare the within-subject differences before and after heat exposure, the index-related heat exposure was collected before and after a routine 5-h work shift and 7-day sailing. Urinary 8-hydroxy-2′-deoxyguanosine (8-OHdG), a useful marker of oxidative DNA damage was the measurement by liquid chromatography/tandem mass spectrometry. The median of the change in urinary 8-OHdG was 0.78?μg/g creatinine, as the urinary 8-OHdG after sailing was significantly higher than before sailing (p?<?0.01). The urinary 8-OHdG was significantly decreased in heat-acclimated boiler tenders. Oxidative DNA damage was significantly decreased in heat-acclimated subjects. Urinary 8-OHdG can be used as a biomarker to assess the effect of heat stress as a result of occupational exposure to extremely high heat conditions.     

The assessment of energy demand in the new olympic windsurf board: Neilpryde RS:X®

The aim of this study was to evaluate the energy demands of sailing the new Neilpryde RS:X Olympic windsurf board. Ten skilled male subjects performed an exhaustive incremental treadmill test to determine their maximal physiological parameters. Thereafter, four tests were performed in a randomised order using two wind conditions, light [2-4 ms(-1) (4-8 knots)] and strong: [9-11 ms(-1)(16-22 knots)]. Oxygen consumption (VO2, ml min(-1) kg(-1)), blood lactate concentration ([la](b), mmol l(-1)), and time spent pumping (% total time) were recorded during 10 min of up-wind leg and during 6 min of down-wind leg. The results indicate that sailing on RS:X is associated with a high level of energy demand using both aerobic and anaerobic pathways whatever the wind conditions. During the down-wind leg, VO2, (ml min(-1) kg(-1)), [la](b) (mmol l(-1)), and time spent pumping (% total time) values for the light and strong wind conditions were 56.5 +/- 5.9 versus 55.5 +/- 3.6; 10.2 +/- 1.5 versus 9.6 +/- 2.3, and 69 +/- 5 versus 64 +/- 2%, respectively. In contrast, during up-wind leg the same parameters for light and strong wind were 53.9 +/- 4.5 versus 40.4 +/- 7.2; 9.7 +/- 2.8 versus 5.0 +/- 2.7 and 66 +/- 3 versus 37 +/- 8%, respectively. During the up-wind leg with strong wind conditions, less time was spent pumping (p < 0.05), mean oxygen consumption values were close to 60% VO2max and post-exercise blood lactate was less than 50% maximal lactate concentration. These results could be related to the time spent in pumping action, involving whole body activity. When sailing with the RS:X board, the physiological demand seems to be higher than with the previous official Olympic windsurf board [Mistral One Design (MOD)]. This difference could be mainly attributed to the specific biomechanical constraints induced by each board characteristic.     

A study of health effects of long-distance ocean voyages on seamen using a data classification approach

Background  

Long-distance ocean voyages may have substantial impacts on seamen's health, possibly causing malnutrition and other illness. Measures can possibly be taken to prevent such problems from happening through preparing special diet and making special precautions prior or during the sailing if a detailed understanding can be gained about what specific health effects such voyages may have on the seamen.     

Simulation of the influence of sports surfaces on vertical ground reaction forces during landing

In many biomechanical analyses, the vertical ground reaction force (GRF) is measured by force plates. However, if force plates are fixed on elastic surfaces, the force signals have low-frequency oscillations superimposed. The question arises, as to whether this oscillation results from the response of the athlete to the surface properties or from the fixation of the force plate on the elastic surface. For the simulation of the vertical GRF, a mechanical model was developed that combines three submodels representing the surface, the athlete and the force plate. The simulations were carried out for landings on concrete and wooden elastic surfaces, without and with the force plate, respectively. Comparison of the two surfaces showed that, on the elastic surface, the passive peak of the vertical GRF was lower and was reached later than on the concrete surface. Thus a lower force rate was possible during the landing on the elastic surface (concrete: 186 body weight per second; wooden: 164 body weight per second), which can reduce the risk of damaging the joint cartilage. The simulations also showed that the time course of the GRF was changed by a rippling effect when the force plate was fixed on the elastic surface. The rippling was not the result of a change in the athlete's movements, because the parameters of the athlete submodel were not changed. The rippling induced by the force plate hinders the analysis of the GRF time course involving the real peak force and the force rate.     

颊侧多曲簧对牙列两侧产生矫治力的对比研究

目的 通过三维测力仪在口外仿真模拟颊侧多曲簧开闭口过程,对其左右两侧产生矫治力进行测量,加以对比研究。方法 用直径为0.8 mm的医用不锈钢丝,由同一人进行弯制,分别弯制左右两侧颊侧多曲簧各5个。将颊侧多曲簧样件固定在三维测力仪上,模拟口内开闭口运动中应力的变化。测量颊侧多曲簧矫治器在开闭口运动中对牙列两侧产生矫治力,对比分析其差异。结果 开闭口运动过程中,左右两侧产生矫治力大小不同,左侧压力最大为（394.36±21.00）g,最大拉力为（134.92±20.81）g,右侧最大压力为（443.04±15.22）g,最大拉力为（144.88±34.62）g。矫治力为0时左右两侧开口度值不一致。结论 颊侧多曲簧对牙列两侧产生矫治力有差异,当颊侧多曲簧产生应力值为0时,右侧开口度与左侧有差异。     

The horizontal vestibulo-ocular reflex during linear acceleration in the frontal plane of the cat

Summary Horizontal and vertical eye movements were recorded in alert, restrained cats that were subjected to whole-body rotations with the horizontal semicircular canals in the plane of rotation and the body centered on the axis or 45 cm eccentric from the axis of rotation. Changes in the horizontal vestibulo-ocular reflex (HVOR) due to the resultant of the linear forces (i.e., gravity and linear acceleration) acting on the otolith organs were examined during off-axis rotation when there was a centripetal acceleration along the animal's interaural axis. The HVOR time constant was slightly shortened when the resultant otolith force was not parallel to the animal's vertical axis. This effect was independent of the direction of the otolith force relative to the direction of the slow phase eye velocity. No effect on the HVOR amplitude was observed. In addition to changes in the HVOR dynamics, a significant vertical component of eye velocity was observed during stimulation of the horizontal canals when the resultant otolith force was not parallel with the animal's vertical axis. The effect was greater for larger angles between the resultant otolith force and gravity. An upward or downward component was elicited, depending on the direction of the horizontal component of eye velocity and the direction of the resultant otolith force. The vertical component was always in the direction that would tend to align the eye velocity vector with the resultant otolith force and keep the eye movement in a plane that had been rotated by the angle between the resultant otolith force and gravity.     

On the Shift from Anticipatory Heart Rate Deceleration to Acceleratory Recovery: Revisiting the Role of Response Factors

The influence of inducing motor responses of low and high force at different times in the cardiac cycle was examined. A handgrip response was used which allowed the separation of response initiation from response completion. Based on earlier work, we expected initiation, rather than completion, to initiate poststimulus cardiac acceleration. We also thought that preparation for a high force response might alter preparatory changes of interbeat interval differently from preparation for a low force response. Fifteen college-aged male subjects performed a warned reaction time task in which a visual stimulus signalled a handgrip requiring either a high or a low force to close. NoGo trials in which an inhibit signal was presented occurred on 12% of the trials. Stimuli occurred either on the R-wave of the electrocardiogram or 300 ms later. Reaction speed was varied in different trial blocks by rewarding response times of 200 ms (+/- 50 ms), 300 ms, or 400 ms. Results based on the timing of response initiation were essentially identical to those based on the timing of response completion. High force relative to low force was associated with both earlier response initiation and earlier cardiac acceleration. Force did not alter preparatory cardiac deceleration. Force and response speed did, however, alter the level of heart rate after response occurrence. Thus, response initiation (or an earlier response process) appears to induce a cardiac acceleration whose level is influenced by the speed and force of the motor response.     

Visual information gain and the regulation of constant force levels

Visual information is essential in human motor control, and especially in the continuous modulation of isometric force. The gain of visual feedback, that is, the amount of space used to represent change in force, has been shown to affect both the magnitude and time-dependent properties of variability in the force output. However, little is known regarding the interacting effects of visual gain and target force level on force variability and whether the effects of force level can be mediated by a gain that is adjusted to force level. We examined the effect of different types and levels of visual feedback gain and target force level (1, 2, 4, 8, and 12 N) on the magnitude (standard deviation, SD) and regularity (approximate entropy, ApEn) of isometric force variability. Young adults performed an isometric force task with high and low levels of constant (same gain level for all forces) and scaled (proportional to force level) gain. The magnitude of force variability increased exponentially as a function of force level once the SD was corrected for the limits of the display area. The time-dependent properties of force variability remained constant across force levels when gain was adjusted to force level. These findings suggest that the time-dependent properties of force variability are the result an interaction between visual feedback and task force level demands, while the increases in SD over force levels are primarily due to the invariant properties of human muscle and the motor system.