气膜厚度对反气泡稳定性的影响

为观察气膜厚度对反气泡稳定性的影响,通过加热反气泡内外溶液来加热气膜内气体从而改变气膜厚度。实验发现:在一定温度范围内,加热反气泡气膜可以延长其稳定时间,但是当加热反气泡气膜使其厚度超过其稳定存在的阈值时,反气泡的稳定性会急剧下降甚至无法产生反气泡;在一定温度范围内温度对溶液表面张力影响很小,这使得文中实验数据合理化。本文为反气泡稳定性的理论研究提供实验支持,并考虑到气膜厚度为微米级,可为微米级气膜传热提供实验素材。     

U型流道中的MHD流动、传热及插件结构的力学性能

结合有限体积法和有限元法研究U型流道中磁流体的流动特性、传热性能和流道插件的力学性能,发现外加磁场强度、金属流体进口速度以及流道插件导电性能对流道内速度场、温度场及流道插件应力、应变场的影响规律。计算结果表明：当外加磁场增强,出口段流场的温度也相应升高;较高的进口速度可以提高出口段流体的温度;提高流道插件导电性能,速度场将呈现“M”型分布,但出口段温度场变化极小。流道插件危险区域位于过渡段侧壁附近,该处应力随磁场增强而增大,随进口速度升高而降低,随流道插件电导率增大略有提升,但都小于插件材料的许用应力。本工作可为ITER包层的设计提供有价值的参考。     

Zeeman磁场对有节点非常规超导体节点结构的影响

在大部分非常规超导体中,准粒子激发谱中存在着“线节点”或“点节点”。 这些节点的存在,导致热力学量和输运系数在低温区的温度变化呈现幂次律。解析分析表明,外加的弱Zeeman磁场会显著影响节点的结构。 尤其是,预言在某些情况下Zeeman磁场可能在费米面上诱导出“面节点”。计算若干自旋单态和自旋三重态的电子比热,结果显示外加的弱Zeeman磁场对节点结构的影响会导致幂次律产生巨大变化。     

Short-term reliability of inflammatory mediators and response to exercise in the heat

Prospective application of serum cytokines, lipopolysaccharide (LPS), and heat shock proteins (eHSPs) requires reliable measurement of these biomarkers that can signify exercise-induced heat stress in hot conditions. To accomplish this, both short-term (7 day) reliability (at rest, n = 12) and the acute responsiveness of each biomarker to exercise in the heat (pre and post 60-min cycling, 34.5°C and 70% RH, n = 20) were evaluated. Serum was analysed for the concentration of C-reactive protein (CRP), interleukin-6 (IL-6), heat shock protein 72 (eHSP72), immunoglobulin M (IgM) and LPS. Test–retest reliability was determined as the coefficient of variation (CV). Biomarkers with the least short-term within-participant variation were IL-6 (19%, ±20%; CV, ±95% confidence limits (CL)) and LPS (23%, ±13%). Greater variability was observed for IgM, eHSP72 and CRP (CV range 28–38%). IL-6 exhibited the largest increase in response to acute exercise (95%, ±11%, P = < 0.001) and although CRP had a modest CV (12%, ±7%), it increased substantially post-exercise (P = 0.02, ES; 0.78). In contrast, eHSP72 and LPS exhibited trivial changes post-exercise. It appears variation of common inflammatory markers after exercise in the heat is not always discernible from short-term (weekly) variation.     

Effects of heat acclimation on hand cooling efficacy following exercise in the heat

This study examined the separate and combined effects of heat acclimation and hand cooling on post-exercise cooling rates following bouts of exercise in the heat. Seventeen non-heat acclimated (NHA) males (mean ± SE; age, 23 ± 1 y; mass, 75.30 ± 2.27 kg; maximal oxygen consumption [VO₂ max], 54.1 ± 1.3 ml·kg^?1·min^?1) completed 2 heat stress tests (HST) when NHA, then 10 days of heat acclimation, then 2 HST once heat acclimated (HA) in an environmental chamber (40°C; 40%RH). HSTs were 2 60-min bouts of treadmill exercise (45% VO₂ max; 2% grade) each followed by 10 min of hand cooling (C) or no cooling (NC). Heat acclimation sessions were 90–240 min of treadmill or stationary bike exercise (60–80% VO₂ max). Repeated measures ANOVA with Fishers LSD post hoc (α < 0.05) identified differences. When NHA, C (0.020 ± 0.003°C·min^?1) had a greater cooling rate than NC (0.013 ± 0.003°C·min^?1) (mean difference [95%CI]; 0.007°C [0.001,0.013], P = 0.035). Once HA, C (0.021 ± 0.002°C·min^?1) was similar to NC (0.025 ± 0.002°C·min^?1) (0.004°C [?0.003,0.011], P = 0.216). Hand cooling when HA (0.021 ± 0.002°C·min^?1) was similar to when NHA (0.020 ± 0.003°C·min^?1) (P = 0.77). In conclusion, when NHA, C provided greater cooling rates than NC. Once HA, C and NC provided similar cooling rates.     

Short-term heat acclimation prior to a multi-day desert ultra-marathon improves physiological and psychological responses without compromising immune status

Multistage, ultra-endurance events in hot, humid conditions necessitate thermal adaptation, often achieved through short term heat acclimation (STHA), to improve performance by reducing thermoregulatory strain and perceptions of heat stress. This study investigated the physiological, perceptual and immunological responses to STHA prior to the Marathon des Sables. Eight athletes (age 42 ± 4 years and body mass 81.9 ± 15.0 kg) completed 4 days of controlled hyperthermia STHA (60 min·day^?1, 45°C and 30% relative humidity). Pre, during and post sessions, physiological and perceptual measures were recorded. Immunological measures were recorded pre-post sessions 1 and 4. STHA improved thermal comfort (P = 0.02), sensation (P = 0.03) and perceived exertion (P = 0.04). A dissociated relationship between perceptual fatigue and T_re was evident after STHA, with reductions in perceived Physical (P = 0.04) and General (P = 0.04) fatigue. Exercising T_re and HR did not change (P > 0.05) however, sweat rate increased 14% (P = 0.02). No changes were found in white blood cell counts or content (P > 0.05). Four days of STHA facilitates effective perceptual adaptations, without compromising immune status prior to an ultra-endurance race in heat stress. A greater physiological strain is required to confer optimal physiological adaptations.     

试论保守力具势的证明

本文借鉴热力学中一种巧妙的证明方法,用直观的物理论证给出了保守力具势的充分性证明,克服了以往在理论力学课程中只有利用复杂的数学工具才能进行充分性证明,学生难以理解的缺点．     

热休克蛋白70及运动对衰老的影响研究

衰老的机制到目前为止没有确切的理论解释,许多研究表明衰老与HSP70的关系密切.论文对HSP70与衰老之间的相互影响及其机制等方面进行了综述,并着重探讨了运动诱导的HSP70对衰老机体的作用,以期为运动延缓衰老提供有力的理论依据.     

运动性延迟性肌肉酸痛与线粒体的热机效率原理的探讨

运动性延迟性肌肉酸痛是一个涉及到全身多个系统,多个层次的综合作用.作为一类特殊类型肌肉疲劳,目前DOMS的研究主要是围绕其产生原因与机理,对机体的影响以及如何有效消除不利因素等方面进行的.本文提出线粒体的热机效率原理可作为DOMS的一种可能性机制的观点,旨在为DOMS的研究深入到分子机制水平指明方向.     

磁场和自由界面热流下二维液态锡膜流的传热模拟

液态金属偏滤器具有自修复和热负荷能力,因此成为偏滤器的重要设计方案。偏滤器上的液态金属膜流处于磁场和高强度热流下,且装置运行时产生的低频扰动会使薄膜流动发展为毛细孤立波。在毛细孤立波膜流中,波谷位置的毛细分离涡会显著增强该区域的对流换热。研究雷诺数为58的液态锡毛细孤立波膜流在底壁附近的换热现象。结果表明：无外加磁场和自由界面热流时,液态锡毛细孤立波薄膜流动复现了努塞尔数在波谷位置显著增强的现象;仅施加磁场时,由于洛伦兹力的阻尼效应,毛细分离涡处的换热增强效果被抑制;仅施加热流时,由于膜流被加热,总换热量增加,导致努塞尔数分布更均匀;同时施加磁场和热流时,两者的作用会叠加。