Clustering Elements of Truss Structures for Damage Identification by CBO

The number of structural elements plays a significant role in detecting damage location and severity; such methods have sometimes failed to provide correct solutions due to the entrapment of damage detection algorithms in the local optimum. To resolve this problem, this study proposed the simultaneous use of mathematical and statistical methods to narrow down the search space. To this end, a two-step damage detection method was proposed. In the first step, the structural elements were initially divided into different clusters using the k-means method. Subsequently, the possibly damaged elements of each cluster were identified. In the second step, the elements selected in the first step were placed in a new set, and a process was applied to identify their respective damage location and severity. Thus, the proposed method reduced the search space as well as the possibility of entrapment in the local optimum. Other advantages of the proposed method include the use of fewer dynamic properties. Accordingly, by narrowing down the search space and the dimensions of the system for governing equations, the proposed method could significantly increase the chance of obtaining favorable results in structures with many elements and those with few vibration modes. A meta-heuristic method, called the colliding bodies optimization (CBO), was used in the proposed damage detection optimization algorithm. The optimization problem was based on the modal strain energy equations. According to the results, the proposed method was able to detect the location and severity of damage, even at its slightest percentage

Brain Activation During Maximum Concentric and Eccentric Knee Extension Muscle Contractions

Purpose: In spite of mounting evidence indicating that concentric and eccentric knee extensor muscle contractions might have special nervous system control strategies, the differentiation of brain frequencies between concentric and eccentric movements and how the motor cortex programs this contraction has been less studied. In this study, the brain and muscle activation differences during maximum concentric and eccentric contractions were compared. Methods: Nine healthy volunteers performed 20 maximum eccentric and 20 maximum concentric knee extensor contractions. Electroencephalography (EEG) signals from sensorimotor-related cortical areas were recorded simultaneous with the electromyography (EMG) of the knee extensor muscles. In the spectral analysis the performance related power values were calculated for Theta (4-7 Hz) and Alpha (7-12 Hz). Results: The time-domain results revealed, longer time and greater cortical activity is required for the preparation of an eccentric contraction. For the eccentric task, the cortical activity was greater, but the EMG was lower in comparison to the concentric task values. Statistical analysis showed significant higher and lower Theta and Alpha power in both types of contractions compared to the resting state, respectively. Conclusion: These findings suggest that increased Theta power is associated with task complexity and focused attention and decreased Alpha power values with increased information processing in the somatosensory cortex

Association between Preparatory Knee Muscle Activation and Knee Valgus Angle during Single Leg Cross Drop Landing Following Anterior Cruciate Ligament Reconstruction

Background: Knee valgus angle seems to be a key factor in both primary– and second–ACL injury risk models. The control of the alignment of the lower limb during dynamic movements depends on the neural activation of the muscles crossing the knee joint prior to the occurrence of stressful events. The current study examined the relationship between the preparatory knee muscle activity and knee valgus angle. Methods: Twenty-eight ACL reconstructed (ACLR) athletes were asked to perform three trials of a single-leg cross drop landing (SCD). Lower extremity kinematics and surface EMG were recorded. Initial contact knee valgus angle and EMG from 100 ms prior to ground contact were used in the data analyses. Results: Preparatory activation medial and lateral hamstring muscles were found to be negatively correlated with knee valgus angle at initial contact (P<0.05). However, the preparatory activity of vastus medialis and vastus lateralis muscles was not associated with initial contact knee valgus angle (P>0.05). Conclusion: The preparatory activity of the knee muscles is linked to knee valgus angle at initial contact, and it may indicate a potential target of second ACL injury prevention programs

Diurnal Cycle of Passive Microwave Brightness Temperatures over Land at a Global Scale

Satellite-borne passive microwave radiometers provide brightness temperature (TB) measurements in a large spectral range which includes a number of frequency channels and generally two polarizations: horizontal and vertical. These TBs are widely used to retrieve several atmospheric and surface variables and parameters such as precipitation, soil moisture, water vapor, air temperature profile, and land surface emissivity. Since TBs are measured at different microwave frequencies with various instruments and at various incidence angles, spatial resolutions, and radiometric characteristics, a mere direct integration of them from different microwave sensors would not necessarily provide consistency. However, when appropriately harmonized, they can provide a complete dataset to estimate the diurnal cycle. This study first constructs the diurnal cycle of land TBs using the non-sun-synchronous Global Precipitation Measurement (GPM) Microwave Imager (GMI) observations by utilizing a cubic spline fit. The acquisition times of GMI vary from day to day and, therefore, the shape (amplitude and phase) of the diurnal cycle for each month is obtained by merging several days of measurements. This diurnal pattern is used as a point of reference when intercalibrated TBs from other passive microwave sensors with daily fixed acquisition times (e.g., Special Sensor Microwave Imager/Sounder, and Advanced Microwave Scanning Radiometer 2) are used to modify and tune the monthly diurnal cycle to daily diurnal cycle at a global scale. Since the GMI does not cover polar regions, the proposed method estimates a consistent diurnal cycle of land TBs at global scale. Results show that the shape and peak of the constructed TB diurnal cycle is approximately similar to the diurnal cycle of land surface temperature. The diurnal brightness temperature range for different land cover types has also been explored using the derived diurnal cycle of TBs. In general, a large diurnal TB range of more than 15 K has been observed for the grassland, shrubland, and tundra land cover types, whereas it is less than 5K over forests. Furthermore, seasonal variations in the diurnal TB range for different land cover types show a more consistent result over the Southern Hemisphere than over the Northern Hemisphere. The calibrated TB diurnal cycle may then be used to consistently estimate the diurnal cycle of land surface emissivity. Moreover, since changes in land surface emissivity are related to moisture change and freeze–thaw (FT) transitions in high-latitude regions, the results of this study enhance temporal detection of FT state, particularly during the transition times when multiple FT changes may occur within a day

Association of Sleep Duration and Quality With Health-Related Quality of Life in Fresher University Students

Background and Objective Sleep duration and quality are important factors for health-related quality of life (HRQoL). This study aimed at investigating the association of sleep duration and quality with HRQoL in fresher students of Neyshabur University of Medical Sciences. Methods The study included 471 fresher students. The sleep duration and sleep quality were measured with the Persian version of Pittsburgh Sleep Quality Index (PSQI) and the HRQoL was evaluated with the Persian version of the 12-Item Short Form Survey (SF-12). The data were collected from late September to early October in 2019 and 2020. The multiple linear regression model was used to determine the independent association of sleep duration and quality with HRQoL. A p-value ≤ 0.05 was considered statistically significant. Results The mean age of the participants was 21.8 ± 6.0 years and the majority of them (62.4%) were female. The total HRQoL score and the prevalence of poor sleep quality were 81.6% and 28.0%, respectively. Among the students, 51.8% and 6.4% reported a sleep duration shorter than 7 hours and equal or more than 9 hours, respectively. The multiple linear regression model showed that excessive sleep duration (≥ 9 h) and sleep quality were associated with Mental Component Summary (MCS) and total HRQoL, respectively (p = 0.036, p = 0.018). Conclusions Referring to the results, enough and quality sleep has beneficial effects on HRQoL in students. Therefore, future strategies should be developed to improve sleep and consequently HRQoL among university students

In vivo fascicle length measurements via B-mode ultrasound imaging with single vs dual transducer arrangements

Ultrasonography is a useful technique to study muscle contractions in vivo, however larger muscles like vastus lateralis may be difficult to visualise with smaller, commonly used transducers. Fascicle length is often estimated using linear trigonometry to extrapolate fascicle length to regions where the fascicle is not visible. However, this approach has not been compared to measurements made with a larger field of view for dynamic muscle contractions. Here we compared two different single-transducer extrapolation methods to measure VL muscle fascicle length to a direct measurement made using two synchronised, in-series transducers. The first method used pennation angle and muscle thickness to extrapolate fascicle length outside the image (extrapolate method). The second method determined fascicle length based on the extrapolated intercept between a fascicle and the aponeurosis (intercept method). Nine participants performed maximal effort, isometric, knee extension contractions on a dynamometer at 10° increments from 50 to 100° of knee flexion. Fascicle length and torque were simultaneously recorded for offline analysis. The dual transducer method showed similar patterns of fascicle length change (overall mean coefficient of multiple correlation was 0.76 and 0.71 compared to extrapolate and intercept methods respectively), but reached different absolute lengths during the contractions. This had the effect of producing force–length curves of the same shape, but each curve was shifted in terms of absolute length. We concluded that dual transducers are beneficial for studies that examine absolute fascicle lengths, whereas either of the single transducer methods may produce similar results for normalised length changes, and repeated measures experimental designs

Age-related changes to motor synergies in multi-joint and multi-finger manipulative skills: a meta-analysis

Purpose The aim of the current meta-analysis was to examine the extent to which there are differences in upper extremity motor synergies across different age groups in manipulative tasks. Methods The studies that used the uncontrolled manifold method to examine the effect of age on motor synergies in multijoint and multi-finger tasks were selected. Sixteen relevant studies from 1154 articles were selected for the meta-analysis—4 and 12 studies considered multi-joint kinematics and multi-finger kinetic tasks respectively. Results The results of the meta-analysis suggested reduced strength of synergies in multi-finger task in older adults, but this was not the case for synergies in multi-joint task. Part of this age-related difference in finger function is related to the increased variability in total force in grasping tasks. However, reductions in the strength of multi-finger synergies in hand functions following ageing appear to depend on the characteristics of the task. Conclusions These findings indicate that the cooperation among fingers to stabilise the total required force to apply for grasping and other fine motor skills is less efficient in older adults that might affect the quality of manipulative tasks

The Effect of Nordic Hamstring Strength Training on Muscle Architecture, Stiffness, and Strength

Purpose: Hamstring strain injury is a frequent and serious injury in competitive and recreational sports. While Nordic hamstring (NH) eccentric strength training is an effective hamstring injury prevention method, the protective mechanism of this exercise is not understood. Strength training increases muscle strength, but also alters muscle architecture and stiffness; all three factors may be associated with reducing muscle injuries. The purpose of this study was to examine the effects of NH eccentric strength training on hamstring muscle architecture, stiffness, and strength. Methods: Twenty healthy participants were randomly assigned to an eccentric training group or control group. Control participants performed static stretching, while experimental participants performed static stretching and NH training for 6 weeks. Pre- and post-intervention measurements included: hamstring muscle architecture and stiffness using ultrasound imaging and elastography, and maximal hamstring strength measured on a dynamometer. Results: The experimental group, but not the control group, increased volume (131.5 vs. 145.2 cm3, p\u3c0.001) and physiological cross-sectional area (16.1 vs. 18.1 cm2, p=0.032). There were no significant changes to muscle fascicle length, stiffness, or eccentric hamstring strength. Conclusions: The NH intervention was an effective training method for muscle hypertrophy, but, contrary to common literature findings for other modes of eccentric training, did not increase fascicle length. The data suggest the mechanism behind NH eccentric strength training mitigating hamstring injury risk could be increasing volume rather than increasing muscle length. Future research is therefore warranted to determine if muscle hypertrophy induced by NH training lowers future hamstring strain injury risk

Longitudinal adaptation of vastus lateralis muscle in response to eccentric exercise

In der vorliegenden Studie wurde daher den Einfluss exzentrischen Trainings, mit unterschiedlicher Reizmagnitude, Bewegungsgeschwindigkeit und Muskellänge bei Reizapplikation, auf die Adaptation des M. vastus lateralis (VL) untersucht. Die 31 Studienteilnehmer wurden randomisiert in zwei Trainings- und eine Kontrollgruppe aufgeteilt. Die Trainingsgruppen führten 30 Trainingseinheiten mit exzentrischem Training der Knieextensoren an einem Isokineten durch. Gruppe 1 (n=10) trainierte ein Bein mit 65% der maximalen willkürlichen isometrischen Kontraktion (MVC) und das andere Bein mit 100% MVC, bei einer Winkelgeschwindigkeit von 90°/s und einem Kniewinkel von 25°-100°. Gruppe 2 (n=10) trainierte beide Beine mit 100% MVC, ein Bein aber mit einer Winkelgeschwindigkeit von 90°/s in einem Kniewinkel von 25°-65° und das andere Bein mit 240°/s und 25°-100°. In der Pre- und Postmessung wurde die VL Muskelfaserlänge mittels Ultraschall bestimmt und die Moment-Winkel- und Leistungs-Winkelgeschwindigkeitsrelation mit einem Dynamometer erfasst. Die Ergebnisse zeigen nur für Bein mit 240°/s eine signifikante (pThe present study investigated the effects of magnitude, velocity and muscle length at which the eccentric stimulus is applied on the longitudinal adaptation of the vastus lateralis muscle (VL). The 31 participants were randomly assigned into two experimental groups to perform 30 sessions of eccentric training for the knee extensors (3 times/week) and one control group. The first experimental group (n=10) exercised one leg at 65% of maximum voluntary isometric contraction (MVC) and the second leg at 100% MVC at 90°/s from 25° to 100° knee angle on an isokinetic device (Biodex 3). The second experimental group (n=10) exercised one leg at 100% MVC at 90°/s from 25° to 65° knee angle and the other leg at 100% MVC at an angular velocity of 240°/s from 25° to 100° knee angle. In pre and post measurements the fascicle length of the VL was examined by ultrasonography and the moment-angle and power-angular velocity relationship of the knee extensors with a dynamometer. The results showed an increase (