Search results for "Mechanical Phenomena"
showing 10 items of 532 documents
Force-, power-, and elasticity-velocity relationships in walking, running, and jumping
1980
Ground reaction forces and mechanical power were investigated when the subjects walked normally, while they were racing or running at four speeds, and when they performed the running long jump take-off. In addition, the apparent spring constants of the support leg in eccentric and concentric phases were investigated at the four running speeds, during the running long jump take-off, and in the triple jump. Six club level track and field athletes, four national level long jumpers, and six national level triple jumpers took part in the study. Cinematographic technique and a mathematical model of hopping (Alexander and Vernon 1975) were employed in the analysis. Force and power values were foun…
Collision with and avoidance of obstacles by blind cave fish Anoptichthys jordani (Characidae).
1985
Blind Mexican cave fish (Anoptichthys jordani) were released into unknown surroundings and their swimming tracks were recorded. During the first 24 h in a new tank, i.e., in unfamiliar environments, the average swimming velocity of the fish was higher than during the remaining time in the tank. Collision with obstacles was recorded by an electrical contact detection method. Single frame analysis of video-recordings revealed that collision can be correlated with tail movements when the fish is close to an obstacle, whereas avoidance correlates with gliding during approach to an obstacle. These behavior patterns are discussed in the context of the flow field hypothesis and inhibition of the l…
Mechanical power and segmental contribution to force impulses in long jump take-off
1979
Changes in total mechanical work, its partitioning into different energy states, mechanical power, force-time characteristics, force impulses of body segments and mass center's pathway characteristics during long jump take-off were investigated on four national and six ordinary level athletes. Both cinematographic and force-platform techniques were used. The data showed that the national level jumpers had higher run-up and higher take-off (release) velocities in horizontal and vertical directions. In addition, they were able to utilize efficiently the elastic energy stored in the leg extensor muscles at take-off impact. This was seen in high support leg eccentric and concentric forces, whic…
Stiff landings are associated with increased ACL injury risk in young female basketball and floorball players
2016
Background: Few prospective studies have investigated the biomechanical risk factors of anterior cruciate ligament (ACL) injury. Purpose: To investigate the relationship between biomechanical characteristics of vertical drop jump (VDJ) performance and the risk of ACL injury in young female basketball and floorball players. Study Design: Cohort study; Level of evidence, 3. Methods: At baseline, a total of 171 female basketball and floorball players (age range, 12-21 years) participated in a VDJ test using 3-dimensional motion analysis. The following biomechanical variables were analyzed: (1) knee valgus angle at initial contact (IC), (2) peak knee abduction moment, (3) knee flexion angle at …
Development of pipette tip-based poly(methacrylic acid-co-ethylene glycol dimethacrylate) monolith for the extraction of drugs of abuse from oral flu…
2019
Abstract In this work, a monolithic polymer based on poly(methacrylic acid-co-ethylene glycol dimethacrylate) (MAA-co-EDMA) was prepared inside 200 μL pipette tips for the extraction of drug of abuse from oral fluid samples. After an appropriate surface tip modification, several polymerization mixtures with different monomer/cross-linker ratios, and percentage of porogen were studied. The most appropriate monolith to easily flow organic solvents and oral fluid samples was prepared with a MAA/EDMA ratio of 8:92 wt/wt and dodecanol containing 10 wt% toluene, as porogenic solvent. Parameters affecting the extraction procedure were evaluated and the monolith was characterized in terms of bindin…
Muscle effort is best minimized by the right-dominant arm in the gravity field
2021
AbstractThe central nervous system (CNS) is thought to develop motor strategies that minimize various hidden criteria, such as end-point variance or effort. A large body of literature suggests that the dominant arm is specialized for such open-loop optimization-like processes whilst the non-dominant arm is specialized for closed-loop control. Building on recent results suggesting that the brain plans arm movements that takes advantage of gravity effects to minimize muscle effort, the present study tests the hypothesized superiority of the dominant arm motor system for effort minimization. Thirty participants (22.5 ± 2.1 years old; all right-handed) performed vertical arm movements between t…
Detecting Ankle Instability With an Instrumented Ankle Arthrometer: An Experimental Study.
2019
A new instrumented device was developed to quantify ankle joint stability during an anterior talar drawer test. The aim of the present study was to validate this device comparing bone kinematics with arthrometer measurement outcomes. An anterior talar drawer test was performed with 14 cadaver legs using a custom instrumented ankle arthrometer. Using clusters of bone-pin markers, the relative three-dimensional movement of calcaneus, talus, and fibula was simultaneously measured. Anterior drawer test was applied on the intact foot and after sequentially sectioning the anterior talofibular ligament, the calcaneofibular ligament, and the posterior talofibular ligament. Cutting the anterior talo…
Technical characteristics can make the difference in a surgical linear stapler. Or not?
2015
Background Anastomotic leak (AL) after gastrointestinal surgery is a severe complication associated with relevant short- and long-term sequelae. Most of the anastomosis are currently performed with a surgical stapler that is required to have appropriate characteristics to guarantee good performances. The aim of our study was to evaluate, in the laboratory, pressure resistance and tensile strength of anastomosis performed with different surgical linear staplers, available in the market. Materials and methods We have been studying three linear staplers, with diverse cartridges and staple heights, of three different companies, used for gastrointestinal anastomosis and gastric or intestinal clo…
Esophageal Biomechanics Revisited: A Tale of Tenacity, Anastomoses, and Suture Bite Lengths in Swine
2019
Background Anastomotic tension has repeatedly been associated with anastomotic leakages after esophagectomy for cancer or esophageal atresia repair. We therefore aimed to determine which anastomotic technique would come as close as possible to the native esophagus in sustaining traction forces. Constant traction for several minutes at esophageal remnants and large suture bites are also considered relevant in long-gap esophageal atresia repair. Methods Porcine esophagi were subjected to linear traction using a motorized horizontal test stand. We compared breaking strengths of native esophagi to simple continuous, simple interrupted, stapled, and barbed suture anastomoses. We also investigate…
Markerless 2D kinematic analysis of underwater running : A deep learning approach
2018
Kinematic analysis is often performed with a camera system combined with reflective markers placed over bony landmarks. This method is restrictive (and often expensive), and limits the ability to perform analyses outside of the lab. In the present study, we used a markerless deep learning-based method to perform 2D kinematic analysis of deep water running, a task that poses several challenges to image processing methods. A single GoPro camera recorded sagittal plane lower limb motion. A deep neural network was trained using data from 17 individuals, and then used to predict the locations of markers that approximated joint centres. We found that 300–400 labelled images were sufficient to tra…