Variation of photovoltage spectra for SnO_2/PS/Si during prior-and post-adsorption

制备了二氧化锡/ 多孔硅/ 硅（SnO2/PS/SI） 异质结构样品，在不同温度下，分别测量样品吸附氢气、液化石油气前后的光生电压谱。结合X 光电子能谱（XPS） 测量结果，分析了光生电压谱变化的机理SnO 2/PS/Si heterojunction structure samples are fabricated.The photovoltage spectra of the samples during prior-and post-adsorption of H 2 or liquified petroleum at different temperature are measured.In combination with the results of XPS measurement,analysis on the variation mechanism of the photovoltage spectra is made.福建省自然科学基

Effects of Knee Osteoarthritis on Body's Center of Mass Motion in Older Adults during Level Walking

Knowledge of the control of the body's dynamic stability in patients with knee osteoarthritis (OA) is helpful for the management of these patients and for the evaluation of treatment outcomes. The purpose of the current study was to investigate the dynamic stability of patients with knee OA during level walking using variables describing the motion of the body's center of mass (COM) and its relationship to the center of pressure (COP). Kinematic and kinetic data during level walking were obtained from 10 patients with bilateral knee OA and 10 normal controls using a motion analysis system and two forceplates. Compared to the normal controls, patients with knee OA exhibited normal COM positions and velocities at key instances of gait but with significant changes in COM accelerations. In the sagittal plane, adjustments to the anterioposterior acceleration of the COM throughout the complete gait cycle were needed for better control of the COM during the more challenging latter half of single leg stance. Diminished A/P COM-COP separation was also used to maintain body stability with reduced joint loadings. In the frontal plane, this was achieved by increasing the acceleration of the body's COM towards the stance leg. The more jerky motion of the body's COM observed may be a result of reduced ability associated with knee OA in the control of the motion of the COM. Strengthening of the muscles of the lower extremities, as well as training of the control of the COM through a dynamic balance training program, are equally important for the dynamic stability of patients with knee OA

Control of body's center of mass motion relative to center of pressure during uphill walking in the elderly

Uphill walking places more challenges on the locomotor system than level walking does when the two limbs work together to ensure the stability and continuous progression of the body over the base of support. With age-related degeneration older people may have more difficulty in maintaining balance during uphill walking, and may thus experience an increased risk of falling. The current study aimed to investigate using gait analysis techniques to determine the effects of age and slope angles on the control of the COM relative to the COP in terms of their inclination angles (IA) and the rate of change of IA (RCIA) during uphill walking. The elderly were found to show IAs similar to those of the young, but with reduced self-selected walking speed and RCIAs (P < 0.05). After adjusting for walking speed differences, the elderly showed significantly greater excursions of IA in the sagittal plane (P < 0.05) and increased RCIA at heel-strike and during single limb support (SLS) and double limb support (DLS) in the sagittal plane (P < 0.05), and increased RCIA at heel-strike in the frontal plane (P < 0.05). The RCIAs were significantly reduced with increasing slope angles (P < 0.05). The current results show that the elderly adopted a control strategy different from the young during uphill walking, and that the IA and RCIA during walking provide a sensitive measure to differentiate individuals with different balance control abilities. The current results and findings may serve as baseline data for future clinical and ergonomic applications. (C) 2015 Elsevier B.V. All rights reserved

Bilateral Knee Osteoarthritis Does Not Affect Inter-Joint Coordination in Older Adults with Gait Deviations during Obstacle-Crossing

Fifteen elderly subjects with bilateral medial knee osteoarthritis (OA) and 15 healthy elderly subjects walked and crossed obstacles with heights of 10%, 20%, and 30% of their leg lengths while sagittal angles and angular velocities of each joint were measured and their phase angles (phi ) calculated. Continuous relative phase (CRP) were also obtained, ie. phi( hip-knee) and phi(knee-ankle). The standard deviations of the CRP curve points were averaged to obtain deviation phase (DP) values for the stance and swing phases. Significant differences between the OA and control groups were found in several of the peak and crossing angles, and angular velocities at the knee and ankle. Both groups had similar CRP patterns, and the DP values of the hip-knee and knee-ankle CRP curves were not significantly different between the two groups. Despite significant changes in the joint kinematics, knee OA did not significantly change the way the motions of the lower limb joints are coordinated during obstacle- crossing. it appears that the OA groups adopted a particular biomechanical strategy among all possible strategies that can accommodate the OA- induced changes of the knee mechanics using unaltered inter-joint coordination control This enabled the OA subjects to accommodate reliably the mechanical demands related to bilateral knee OA in the sagittal plane during obstacle-crossing. Maintaining normal and reliable inter- joint coordination may be considered a goal of therapeutic intervention, and the patterns and variability of inter- joint coordination can be used for the evaluation of treatment effects

Redistribution of intra- and inter-limb support moments during downhill walking on different slopes

Downhill walking presents a greater risk of falling as a result of slipping or loss of balance in comparison with level walking. The current study aimed to investigate the effects of inclination angles on the intra-limb (inter-joint) and inter-limb sharing of the body support during downhill walking for a better understanding of the associated control strategy. Fifteen young male adults (age: 32.6 + 5.2 years, height: 168.9 +/- 5.5 cm, mass: 68.4 +/- 8.7 kg) performed level and downhill walking while their kinematic and kinetic data were measured for calculating joint moments and total support moments of the lower limbs using inverse dynamics analysis. The peak total support moments of both the leading and trailing limbs increased with increasing inclination angles (p < 0.05) with different sharing patterns among individual joints. Being the major contributor to the peak total support moment during early single-limb support, the contribution of the knee remained unaltered (p > 0.05), but the contributions of the hip increased with reduced contributions from the ankle (p < 0.05). For the increased peak total support moment during late single-limb support, the intra-limb sharing changed from a major ankle contribution to a major knee contribution strategy. The hip contribution was also increased (p < 0.05) but the hip flexor moment remained unaltered (p > 0.05). During double-limb support, the main contributor to the whole body support changed from the trailing limb to the leading limb with increasing inclination angles (p < 0.05). (C) 2013 Elsevier Ltd. All rights reserved

Balance Control and Inter-Joint Coordination in Patients with Degenerative Knee Osteoarthritis During Obstacle-Crossing

中文摘要化性膝關節炎是中老年人最常見的關節炎。關節在長期承受重力及運動下，關節軟骨會退行性病變，連帶引起軟骨下硬骨增厚、關節變形、滑液膜和關節周圍結構相關變化的疾病，並失去彈性，進而發生關節疼痛、腫脹、僵硬、變形的情形，以致活動受限，罹患退化性關節炎之老人跨越障礙物之跌倒危險性增加，且可能造成嚴重後果。於跨越障礙物時平衡控制及關節間協調之研究有助於設計預測或預防跌倒之方法。本研究利用一配有七台紅外線攝影機之動作分析系統量測受測者跨越三種高度障礙物（10%、20% 及30％腳長）時全身之運動學資料，並利用兩塊測力板量測地面反作用力。本研究先建立年輕人及健康老年人跨越不同高度障礙物時之平衡控制資料，並以此為基礎進一步探討患退化性膝關節炎之老年人跨越不同高度障礙物時平衡控制及關節間協調，以瞭解退化性膝關節炎對行走跨越障礙物之影響。結果顯示面對不同高度的障礙物，健康年輕人利用調節垂直方向之身體質量重心位置，速度，及加速度來維持平衡控制。此外，身體質量重心之左右方向加速度隨著高度增加而增加，顯示左右方向之肌力在單腳支撐及雙腳支撐轉換時需用以調控已達成平順的重心位置轉移。如果因為左右方向之肌力及協調不足，則可能在跨越較高的障礙物時發生跌倒。前後方向之加速度也使前後方向身體質量重心及足底壓力中心之距離隨著障礙物高度增加而降低。關於老年人的平衡控制研究結果顯示，在跨障礙物的各關鍵時刻，老年人有較小的向內身體質量重心及足底壓力中心之角度，因此神經肌肉骨骼系統會有較多的餘力來控制擺盪腳之終端點控制。不論是年輕人或是老年人皆利用降低體質量重心及足底壓力中心之角度的策略來增加身體的穩定性。患退化性膝關節炎之老年人在行走時可以維持正常之身體質量重心之位置及速度，然後走路過程的加速度變化卻顯著較大。也許是因為患退化性膝關節炎之老年人控制身體重心的能力不足而產生這種比較不穩定的動作特徵。為了能夠維持單腳支撐後期較高的挑戰，前後加速度在整個步態過程當中都在作調控。前後方向身體質量重心及足底壓力中心之距離之降低，是患退化性膝關節炎之老年人為了降低膝關節負荷所採取的保守策略。在額狀面上，這個保守的策略也藉由增加身體質量中心向支撐腳的加速度來達成。當比較走路及跨障礙物這兩個任務身體質量中心之表現時，則發現身體質量中心與足底壓力中心之傾斜角度及角速度需要在面對跨障礙物時作必要的調節，尤其是在單腳支撐及雙腳支撐轉換時。其中患退化性膝關節炎之老年人不論是在走路或跨障礙物，其矢狀面上身體質量中心控制與拇指終端點與地面之距離皆能保持正常。患退化性膝關節炎之老年人在由單腳支撐至雙腳支撐轉換時，向前之能夠藉由降低身體質量中心與足底壓力中心之向前傾斜角度，並在由雙腳支撐至單腳支撐轉換時增加身體質量中心與足底壓力中心之向前傾斜角速度來維持轉換之間的穩定。即使先前之研究發現為了減少膝關節負荷及相關之疼痛，退化性膝關節炎老人作了一些下肢關節運動的改變，但是至於其關節間的協調卻沒有顯著的改變。有此顯示在跨越障礙物時，退化性膝關節炎老人在矢狀面上能穩定地應付雙腳退化所造成的負荷。保持正常且穩定之關節間協調可以用來當作治療介入的成效。而關節間協調之型態及變異性亦可用來評估治療效果。Osteoarthritis (OA), defined by degradation of the articular cartilage and an increase in subchondral bone density, is a common joint disorder in the elderly. Knee OA has also been associated with falls in the elderly. Knee OA has been reported to affect the performance of ambulation, including level walking and obstacle-crossing. An increased risk of falling in patients with knee OA during obstacle-crossing, as opposed to unobstructed level walking, may be explained by the difference in the control of the body’s center of mass (COM) with respect to the center of pressure (COP) while trying to ensure sufficient foot clearance. Knowledge of the control of the body’s dynamic stability in patients with knee OA is helpful for the management of these patients and for the evaluation of treatment outcomes. In the present study, young, older and knee osteoarthritic subjects were recruited to investigate the influence of aging and aging-related disease on the balance control and inter-joint coordination of obstacle-crossing using motion analysis techniques. In young subject, it was found that vertical components of the COM motion, including position, velocity and acceleration, were all modulated to successfully cross obstacles of different height and that these modulations were different between the leading and trailing limbs. Since the acceleration of the COM is directly related to the forces applied to the COM, the increase in the magnitude of the M/L acceleration of the COM with increasing obstacle height suggests that increased forces from muscle contractions are required to ensure the control of the smooth transition of the COM position between single and double stance phase. If the M/L stability is compromised, due to muscle weakness or degradation of coordination, falls may occur. Whole body control through adjustments of the A/P acceleration of the COM to reduce A/P COM-COP distances was required for the necessary stability in the sagittal plane when crossing obstacles of increased height. For the elderly, at this critical time during obstacle-crossing the older group used smaller medial COM-COP inclination angles to cross the obstacle successfully without falling sideways, suggesting that the neuromusculoskeletal system may have more room to control the swing foot with sufficient foot clearance. Decreased inclination angles with increasing obstacle height suggest that the subjects tended to keep their COM position close to the COP position to increase the body’s stability. For the patients with knee OA, normal COM positions and velocities were found at key instances during the walking cycle but with significant changes in COM accelerations. This more jerky motion of the body’s COM may be a result of reduced ability associated with knee OA in the control of the motion of the COM. For better control of the COM in the A/P direction during the more challenging latter half of SLS, adjustments to the A/P acceleration of the COM throughout the complete gait cycle were needed. Diminished A/P COM–COP separation was a conservative strategy for patients with knee OA in order to maintain body stability with reduced joint loadings. In the frontal plane, this was achieved by increasing the acceleration of the body’s COM towards the stance leg. Strengthenging of the muscles of the lower extremities, as well as training of the control of the COM through a dynamic balance training program, are equally important for the dynamic stability of patients with knee OA. When comparing body’s center of mass motion during unobstructed with those during obstructed gait in patients with knee osteoarthritis, modulation of inclination angle and angular velocities were necessary when facing more challenging tasks such as obstacle-crossing, particularly so in patients with knee OA. While less stable COM control was found around the end stage of double stance phase during obstacle-crossing when compared to level walking, patients with knee OA successfully acquired strategies in the sagittal plane to maintain close-to-normal stable COM control with normal toe clearance during both level walking and obstacle-crossing. They achieved stable transitions from SLS to DLS through a reduced anterior inclination angle and from DLS to SLS through an increased anterior angular velocity. It is suggested that assessment of the ability to control dynamic stability in patients with knee OA should consider both the positions and velocities of the COM and the COP. For the inter-joint coordination, despite significant changes of the joint kinematics knee OA did not change significantly the way the motions of the lower limb joints are coordinated during obstacle-crossing. It appears that the OA group had adopted a particular biomechanical strategy among all possible strategies that can accommodate the OA-induced changes in the knee mechanics using unaltered inter-joint coordination control. This enabled the OA subjects to accommodate reliably the mechanical demands related to bilateral knee OA in the sagittal plane during obstacle-crossing. Maintaining normal and reliable inter-joint coordination could be considered as an outcome of therapeutic intervention, and the patterns and variability of inter-joint coordination can be used to evaluate treatment effects.Table of Contents文摘要 ibstract ivist of Tables ivhapter 1 Introduction 1.1. Knee Osteoarthritis 1.2. Obstacle-Crossing During Level Walking 1.3. Strategies of Obstacle-Crossing in Young Adults 4.3.1. Roles of the Leading and Trailing Limb 5.3.2. Peak vs. Crossing Moments 6.3.3. Obstacle Height Effects 6.4. Biomechanics of Obstacle-Crossing in Older Adults 10.5. Lower Limb Mechanics of Walking and Obstacle-Crossing in Patients with Knee OA 13.5.1. Effects of Knee OA on the Joint Mechanics During Level Walking 13.5.2. Effects of Knee OA on the Joint Mechanics During Obstacle-Crossing 15.5.3. Limitations of the Previous Studies on Knee OA During Level Walking and Obstacle-Crossing 16.6. Balance Control in Terms of Body’s COM Motion 17.7. Inter-joint Coordination During Obstacle-Crossing 20.8. Limitations of Previous Studies 23.9. Aims of This Dissertation 26hapter 2 Materials and Methods 28.1. Subjects 28.1.1. Young Subjects 28.1.2. Older Subjects 29.1.3. Older Subjects with Knee OA 30.2. Instruments 33.3. Experiments 34.4. Biomechanical Analysis Models 37.4.1. Coordinate Systems 37.4.2. Anthropometric Parameters 42.4.3. Inverse Dynamics Analysis 42.4.4. Body’s COM Model 49.5. Data Analysis 52.5.1. Definition of the Crossing Cycles 52.5.2. End-Point Variables and Crossing Speed 53.5.3. Joint Kinematics 54.5.4. Joint Kinetics and GRF 55.5.5. COM Variables 56.5.6. Inter-Joint Coordination 57.5.7. Statistical Analysis 60hapter 3 Effects of Obstacle Height on the Control of the Body’s Center of Mass Motion During Obstructed Gait 62.1. Data Analysis 63.2. Results 65.3. Discussion 75.4. Conclusion 80hapter 4 Age and Height effects on the Center of Mass and Center of Pressure Inclination Angles During Obstacle-Crossing 81.1. Data Analysis 83.2. Results 85.3. Discussion 93.4. Conclusion 97hapter 5 Effects of Knee Osteoarthritis on Body’s Center of Mass Motion in Older Adults During Level Walking 98.1. Data Analysis 99.2. Results 100.3. Discussion 108.4. Conclusion 112hapter 6 Control of Body’s Center of Mass Motion During Unobstructed and Obstructed Gait in Patients with Knee Osteoarthritis 113.1. Data Analysis 114.2. Results 116.3. Discussion 126.4. Conclusion 129hapter 7 Bilateral Knee Osteoarthritis Does Not Affect Inter-Joint Coordination in Older Adults with Gait Deviations During Obstacle-Crossing 130.1. Data Analysis 132.2. Results 133.3. Discussion 144.4. Conclusion 147hapter 8 Conclusions and Suggestions 148.1. Conclusions 149.1.1. Effects of Obstacle Height on the Control of the Body’s Center of Mass Motion During Obstructed Gait 149.1.2. Age and Height effects on the Center of Mass and Center of Pressure Inclination Angles During Obstacle-Crossing 150.1.3. Effects of Knee Osteoarthritis on Body’s Center of Mass Motion in Older Adults During Level Walking 151.1.4. Control of Body’s Center of Mass Motion During Unobstructed and Obstructed Gait in Patients with Knee Osteoarthritis 152.1.5. Bilateral Knee Osteoarthritis Does Not Affect Inter-Joint Coordination in Older Adults with Gait Deviations During Obstacle-Crossing 153.2. Suggestions for Further Studies 154eferences 15

Biomechanical Role of the Locomotor System in Controlling Body Center of Mass Motion in Older Adults during Obstructed Gait

Fifteen young and fifteen older healthy adults walked and crossed obstacles of three different heights while kinematic data and ground reaction forces were acquired to calculate the three-dimensional motion of the centre of mass (COM) and lower limb joint moments. The older group had greater normalized jerk score of the COM. When the leading limb was crossing, the older group kept the COM more posterior and on the trailing stance limb for longer with increased knee extensor crossing moments and thus decreased anterioposterior COM deceleration. When the trailing limb was crossing, the older group decreased vertical COM deceleration through increased hip extensor crossing moments . The older group maintained the same COM motion as the young in the frontal plane with greater hip and knee abductor crossing moments. The older group exhibited significant kinetic changes in their locomotor system with increased muscular demand, leading to a more jerky motion of the body COM. However, these changes helped to maintain the frontal COM motion and to achieve a sagittal COM motion pattern which is thought to be helpful for a safe and successful obstacle-crossing. Failure to meet the kinetic demands in the elderly may increase the risk of falls during obstacle-crossing