不同输出电压对激光焊接钴铬合金焊件疲劳强度的影响

目的:探讨不同输出电压对激光焊接钴铬合金试件机械强度和疲劳强度的影响。方法:将牙科钴铬合金采用激光焊接在分别在220 V、250 V、280 V三种输出电压下焊接成哑铃形试件(n=10),以未焊接组作为对照,在材料测试机上进行三点弯曲试验,记录试件的最大压应力值和疲劳强度,并对断口进行显微晶相分析。结果:各焊接组的最大压应力值均小于未焊接组,其中220 V组最小,250 V组与280 V组的差别无显著性;各焊接组的疲劳强度随着输出电压的升高而升高,差异有显著性,但各焊接组的疲劳强度均远小于未焊接组。结论:在一定范围内,激光焊接的疲劳强度随输出电压的升高而增大。     

酸碱度对Vitallium与钴铬合金卡环疲劳强度影响的比较

目的:比较高钴铬钼合金(Vitallium 2000 plus,V)与钴铬合金(WBA,W)卡环臂在不同酸碱度下相同形变及循环次数时的疲劳衰减。方法:分别铸造V与W直型卡环臂20个,分别置于空气和pH值4.0、6.7和8.0的人工唾液中。用万能试验机进行0.8 mm变形的循环加载20000次,得到载荷-时间曲线算出试件的衰减百分数。扫描电镜观察表面。结果:W各组衰减均高于V,在空气中衰减最小,随实验组pH值增大试件衰减增大;V在pH=4组衰减最多。结论:使用Vitallium 2000 plus铸造可摘局部义齿的卡环可保持更长时间的初始修复效果。     

Effect of muscle fatigue on the sense of limb position and movement

We have recently shown that in an unsupported forearm-matching task blindfolded human subjects are able to achieve an accuracy of 2–3°. If one arm was exercised to produce significant fatigue and the matching task was repeated, it led subjects to make position-matching errors. Here that result is confirmed using fatigue from a simple weight-lifting exercise. A 30% drop in maximum voluntary force after the exercise was accompanied by a significant matching error of 1.7° in the direction of extension when the reference arm had been fatigued, and 1.9° in the direction of flexion when the indicator arm had been fatigued. We also tested the effect of fatigue on a simple movement tracking task where the reference forearm was moved into extension at a range of speeds from 10 to 50°s⁻¹. Fatigue was found not to significantly reduce the movement-tracking accuracy. In a second experiment, movement tracking was measured while one arm was vibrated. When it was the reference arm, the subject perceived the movement to be significantly faster (3.7°s⁻¹) than it actually was. When it was the indicator, it was perceived to be slower (4.6°s⁻¹). The data supports the view that muscle spindles are responsible for the sense of movement, and that this sense is not prone to the disturbance from fatigue. By contrast, the sense of position can be disturbed by muscle fatigue. It is postulated, that the sense of effort experienced by holding the arm against the force of gravity is able to provide information about the position in space of the limb and that the increased effort from fatigue produces positional errors.     

Contralateral muscle fatigue in human quadriceps muscle: evidence for a centrally mediated fatigue response and cross-over effect

The purpose of this investigation was to examine the effects of voluntary muscular fatigue in one lower limb and determine whether a ‘cross-over’ of fatigue is evident in the contralateral limb. Twenty-eight subjects (13 males and 15 females) performed a series of voluntary and evoked isometric contractions of both the dominant (exercised) and non-dominant (non-exercised) leg extensor muscles, prior to and after a fatigue protocol consisting of a 100-s sustained maximal isometric contraction (MVC) performed by the dominant limb only. Force values and surface electromyography (EMG) from the vastus lateralis muscle were obtained allowing for the determination of twitch and compound action potential (M-wave) values. Maximal twitch tension and peak-to-peak amplitude were significantly decreased after the fatigue test in the dominant limb, as was maximal voluntary force (∼65 N reduction), EMG activity (∼0.1 mV decrease) and voluntary activation (∼17% decline). However, no significant changes were observed in the non-dominant limb with respect to twitch and M-wave properties nor in MVC force. The voluntary activation of the non-dominant limb decreased significantly by 8.7% after the fatigue test, which was performed only on the dominant limb. The results of the present study suggest that the decrease in force production in the exercised limb was primarily related to peripheral fatigue mechanisms, with central fatigue making a lesser contribution. Centrally mediated mechanisms appear to be the sole contributor to fatigue in the non-exercised limb suggesting an anticipatory fatigue response and a ‘cross-over’ of central fatigue between the exercised and non-exercised contralateral limb.     

Lactate is a metabolic substrate that sustains extraocular muscle function

Lactic acid is considered the end product of glycolysis and is a major cause of muscle fatigue. However, the lactate dehydrogenase (LDH) reaction is bidirectional: Lactate can be oxidized to pyruvate and used as a substrate for the Krebs cycle. Therefore, our hypothesis was that lactate sustains the contractile function of rat extraocular muscles during periods of increased activity. The study used extraocular and extensor digitorum longus (EDL) muscles from adult Sprague–Dawley rats to determine LDH isoform expression, total LDH activity, and contractile function in vitro. To evaluate the role of lactate on fatigue, we tested the effect of cinnamate, a blocker of lactate transport, and exogenous lactate on fatigue resistance. Cinnamate accelerated fatigue in the extraocular muscles: Endurance and residual force decreased significantly. Conversely, cinnamate did not affect the endurance or residual force of EDL muscles. Replacing glucose with exogenous lactate increased EDL fatigability but had no effect on the extraocular muscles. However, the extraocular muscles fatigued faster when exposed to exogenous lactate combined with cinnamate. The LDH-A and LDH-C isoforms were expressed at lower levels in extraocular muscle; LDH-B was equally abundant in the EDL and extraocular muscles. Total LDH activity in the extraocular muscles was only approximately 32% of the level in EDL. These results support the hypothesis that lactate sustains the contractile performance of the extraocular muscles.     

The effect of exercise counselling with feedback from a pedometer on fatigue in adult survivors of childhood cancer: a pilot study

Objective  The aim of this study was to evaluate the results of home-based exercise counselling with feedback from a pedometer on fatigue in adult survivors of childhood cancer. Patients  Adult survivors of childhood cancer were recruited from the long-term follow-up clinic of the University Medical Centre Groningen, The Netherlands. A score of 70 mm on a visual analogue scale (scale, 0–100 mm) for fatigue was used as an inclusion criterion. Controls were recruited by the survivors among their healthy siblings or peers. Methods  During 10 weeks, the counselor encouraged the survivors to change their lifestyle and enhance daily physical activity such as walking, cycling, housekeeping and gardening. As a feedback to their physical activity, the daily number of steps of each survivor was measured by a pedometer and registered using an online step diary at the start of the programme and after 4 and 10 weeks. Fatigue was the primary outcome measure, assessed with the Checklist Individual Strength (CIS) at start (T0), 10 weeks (T10) and 36 weeks (T36). Thirty-three healthy age-matched control persons were asked to complete the CIS. Results  Out of 486 cancer survivors, 453 were interested and were asked to complete the VAS to measure fatigue; 67 out of 254 respondents met the inclusion criteria, 21 refused, 46 were enrolled and eight dropped out during the study. The mean scores on the CIS in the survivors at T0 was 81.42 (SD ± 20.14) and at T10 62.62 (SD ± 20.68), which was a significant improvement (p < 0.0005). At T36, the end of the study, the mean CIS score was 63.67 (SD ± 23.12); this was a significant improvement compared with the mean CIS at the start (p < 0.0005). There was no significant difference in the mean CIS scores of the controls during the follow-up period. Conclusion  The stimulation of daily physical activity using exercise counselling and a pedometer over 10 weeks leads to a significant decrease in fatigue in adult survivors of childhood cancer, and this improvement lasts for at least 36 weeks.     

口腔修复体疲劳抗性测试机的研制

目的研制可以模拟口腔咬合和咀嚼的修复体疲劳抗性测试机,以测试修复体疲劳抗性。方法通过偏心轴承的圆周运动产生偏心行程,将圆周运动转化为往复运动。偏心轴承通过钢丝绳与加载端相连,由电机带动偏心轴承转动从而产生偏心行程,加载端模拟口腔的咬合和咀嚼运动实现循环加载。结果进行200万次试运行,各部件运行状态良好。结论本实验中的修复体疲劳抗性测试机可以满足模拟口腔功能实验需要。     

Comparing effects of aromatherapy with lavender essential oil and orange essential oil on fatigue of hemodialysis patients: A randomized trial

Background and purposeFatigue is a common complication of hemodialysis. This study aimed to compare the effects of aromatherapy with essential oils of lavender and orange on the fatigue of hemodialysis patients.Materials and methodsNinety subjects were randomly allocated into three groups of aromatherapy with lavender essential oil, aromatherapy with orange essential oil and control. Data collection tool was the Fatigue Severity Scale. In each experimental group, subjects inhaled five drops of lavender essential oil and orange essential oil.ResultsThe difference in the mean of fatigue before and after the intervention in each of the experimental groups was statistically significant, but this difference was not significant in the control group. Between the two groups of aromatherapy, no significant difference was observed in terms of the mean fatigue after the intervention.ConclusionAromatherapy with lavender essential oil and orange essential oil might reduce fatigue in hemodialysis patients.     

耳穴埋籽配合五行音乐疗法在血液透析疲劳患者中的应用效果观察

目的：评价耳穴埋籽配合五行音乐在血液透析疲劳患者中的应用效果。方法：将60例血液透析疲劳患者随机分为观察组和对照组,各30例,对照组采用常规护理,观察组除常规护理外,给予耳穴埋籽配合五行音乐干预。两组在干预前后采用修改版多维疲劳量表（multidimensional fatigue inventory-20,MFI-20)和肾脏病相关生活质量评价量表（KDQOL-SFTM）评价患者疲劳程度和生活质量。结果 干预后,观察组疲劳三个维度（心理疲劳、躯体疲劳、活动减少）得分均低于对照组,差异有统计学意义（P＜0.01）;生活质量13个维度得分均高于对照组,差异有统计学意义（P＜0.05）。结论：耳穴埋籽配合五行音乐可有效缓解血液透析患者疲劳程度,改善生活质量,且该疗法操作简便、经济安全,患者易于接受。     

湖南省某市护士共情疲劳的影响因素分析

目的 分析临床护士共情疲劳的影响因素,为预防护士职业倦怠和二次创伤提供理论依据。方法 采用一般资料量表、共情疲劳简短版量表对某市6家医院共1012名护士进行调查,探索影响护士共情疲劳的因素。结果 ①本次调查临床护士年龄在19~55岁,平均年龄（30.10±7.09）岁,其中男9名（0.89%）,女1003名（99.11%）,独生子女216名（21.34%）,非独生子女796名（78.65%）;②独生子女、每月夜班9个及其以上、经历职业暴露和医患纠纷3次及以上、健康状况和睡眠质量很差是共情疲劳得分较高的群体,差异均有统计学意义（P＜0.05）。结论 独生子女、每月夜班数及经历职业暴露越多、自身健康状况越差的护理人员共情疲劳水平越高,应针对此类人群进行重点预防。