The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform
S P Magnusson - One of the best experts on this subject based on the ideXlab platform.
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determinants of musculoskeletal flexibility viscoelastic properties cross Sectional Area emg and stretch tolerance
Scandinavian Journal of Medicine & Science in Sports, 2007Co-Authors: S P Magnusson, Erik B Simonsen, Per Aagaard, J Boesen, Finn Johannsen, Michael KjaerAbstract:Cross-Sectional Area, stiffness, viscoelastic stress relaxation, stretch tolerance and EMG activity of the human hamstring muscle group were examined in endurance-trained athletes with varying flexibility. Subjects were defined as tight (n = 10) or normal (n = 8) based on a clinical toe-touch test. Cross-Sectional Area was computed from magnetic resonance imagining (MRI) images. Torque (Nm) offered by the hamstring muscle group, electromyographic (EMG) activity, knee joint angle and velocity were continuously monitored during two standardized stretch protocols. Protocol 1 consisted of a slow stretch at 0.087 rad/s (dynamic phase) to a pre-determined final angle followed by a 90-s static phase. In the dynamic phase final angle and stiffness was lower in tight (28.0+/-2.9 Nm/rad) than normal subjects (54.9+/-6.5 Nm/rad), P<0.01. In the static phase tight subjects had lower peak (15.4+/-1.8 Nm) and final torque (10.8+/-1.6 Nm) than normal subjects (31.6+/-4.1 Nm, 24.1+/-3.7 Nm, respectively)(P<0.01), but torque decline was similar. Protocol 2 consisted of a slow stretch to the point of pain and here tight subjects reached a lower maximal angle, torque, stiffness and energy than normal subjects (P<0.01). On the other hand, stiffness was greater in tight subjects in the common range (P<0.01). Cross-Sectional Area of the hamstring muscles and EMG activity during the stretch did not differ between the groups. However, lateral hamstring cross-Sectional Area was positively related to mid-range stiffness (P<0.05), but inversely related to final stiffness, peak torque and the toe-touch test (P<0.01). Final angle and peak torque in protocol 1 combined to improve the predictability of the toe-touch test (R2=0.77, P<0.001). These data show that the toe-touch test is largely a measure of hamstring flexibility. Further, subjects with a restricted joint range of movement on a clinical toe-touch test have stiffer hamstring muscles and a lower stretch tolerance.
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effect of habitual running on human achilles tendon load deformation properties and cross Sectional Area
Journal of Applied Physiology, 2003Co-Authors: Philip Hansen, Michael Kjaer, Per Aagaard, B Larsson, S P MagnussonAbstract:Whether the cross-Sectional Area (CSA) and mechanical properties of the human Achilles tendon change in response to habitual exercise remains largely unexplored. The present study evaluated the CSA...
Fuqian Yang - One of the best experts on this subject based on the ideXlab platform.
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Mechanical properties of Cu nanowires: Effects of cross-Sectional Area and temperature
Materials Science and Engineering: A, 2020Co-Authors: Hui Cao, Zhiyuan Rui, Fuqian YangAbstract:Abstract Nanostructured materials likely exhibit different mechanical properties from the corresponding bulk materials and have potential applications in a variety of Areas. In this work, we use molecular dynamics simulation with embedded-atom potential to investigate the dependence of the mechanical properties of Cu nanowires of square cross-section, including Young's modulus, yield stress and surface force, on cross-Sectional Area and temperature for the Cu nanowires with cross-Sectional Areas in a range of 13.1 to 117.6 nm2 in a temperature range of 100 to 500 K. The simulation results reveal that the Young's modulus increases with the increase of the cross-Sectional Area at the same temperature and decreases with the increase of temperature for the same cross-Sectional Area. The yield stress decreases with the increase of the cross-Sectional Area at the same temperature in the range of 100 to 400 K and increases with the increase of the cross-Sectional Area at 500 K, while it decreases with the increase of temperature for the same cross-Sectional Area. The surface force decreases with the increase of the cross-Sectional Area at the same temperature and with the increase of temperature for the same cross-Sectional Area. Semi-empirical expressions relating the mechanical properties to temperature are proposed. Using the semi-empirical expressions, the Young's modulus at 0 K is found to decrease with the decrease of the cross-Sectional Area, and the yield stress at 0 K is found to decrease linearly with the increase of the cross-Sectional Area.
Koichi Goda - One of the best experts on this subject based on the ideXlab platform.
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Tensile properties of natural fibers with variation in cross-Sectional Area
Advanced Composite Materials, 2014Co-Authors: Junji Noda, Yujiro Terasaki, Yuji Nitta, Koichi GodaAbstract:Natural fiber-reinforced green composites are increasingly being used in various industries. Generally speaking, the cross sections of natural fibers are not circular. Moreover, they show wide variation in their cross-Sectional Area. Nevertheless, the tensile properties of natural fibers are often evaluated on the assumption of a circular cross-Sectional shape. Therefore, we proposed a new method to calculate the natural fiber cross-Sectional Area by measuring their projection widths to estimate the proper tensile properties. This method was used to investigate the effects of cross-Sectional Area variation on tensile properties. Additionally, to estimate the proper Weibull parameters of natural fibers apart from the cross-Sectional Area variation, we proposed a strength distribution function that incorporates cross-Sectional Area variation, based on a Weibull distribution. Finally, we formulated a strength distribution function of natural fibers that includes the cross-Sectional Area variation.
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Cross-Sectional Area evaluation and tensile properties of alkali-treated kenaf fibres
Composites Part A: Applied Science and Manufacturing, 2013Co-Authors: Y. Nitta, Junji Noda, Koichi Goda, W-il LeeAbstract:Abstract A cross-Sectional Area evaluation method for multi-cell type natural fibres treated in a highly concentrated alkali solution was proposed using kenaf fibres. Cross-section of kenaf fibres was drastically changed by the alkali treatment compared to the untreated fibres. Conventional data-based approximation (DBA) method for evaluating cross-Sectional Area was not sufficient, because it was based on cross-Sectional Area data of the untreated fibres. DBA was modified on the assumption that the shape of each cell in the alkali-treated fibres was an ellipse, and again correlated with hexagonal cross-Sectional Area, which was approximated by measuring the projection widths on the fibre along 0°, 60° and 120° directions. This is the new data-based approximation method (DBA-AT). Results showed that the tensile strength was greatly improved, compared to the strength values estimated by untreated fibre-based DBA. Especially, tensile strength of alkali-treated fibre on the condition of 15 wt%NaOH for 1 h was comparable to untreated fibre.
John S. Wheeler - One of the best experts on this subject based on the ideXlab platform.
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Urodynamic measure of urethral cross-Sectional Area: application for obstructive uropathy.
Neurourology and urodynamics, 1994Co-Authors: James S. Walter, John S. Wheeler, Paul Zaszczurynski, Michael PlishkaAbstract:A conductance formula was developed based on pressure (P) and flow (Q) data collected from rigid tubes with a cross-Sectional Area in the range of the flow controlling zone of the urethra. Curve fitting of data resulted in an exponential formula and a simple proportionality constant related tube of differing cross-Sectional Area. The resulting formula estimates cross-Sectional Area based on P and Q data and is in the form of a conductance ratio because Q is in the numerator and P is in the denominator. The formula is AEFm = 3.5 Q/P0.58, where AEFm is the Area equivalent factor-male and Q is measured in ml/sec and P is cm H2O. To further introduce the estimate of cross-Sectional Area, urodynamics were retrospectively reviewed from 19 males over the age of 50 with complaints of prostatism. The AEFm was plotted on standard urodynamic records much like P and Q data. The onset of voiding was characterized by a rapid increase in urethral Area. Maximal cross-Sectional Area obtained at maximal flow was 2.9 +/- 1.4 mm2. The maximal urethral Area per unit of applied detrusor pressure, an estimate of urethral compliance, was 0.06 +/- 0.6 mm2/cm H2O. This latter measure may help to compare patients with widely different detrusor pressures. The urodynamic data from two young adult males is also presented for comparison. Their average maximal urethral cross-Sectional Area was 7.1 mm2. Their average Area per unit of applied detrusor pressure was 0.15 mm2/cm H2O. These larger values contrast sharply with the BPH group. The AEFm clearly shows urethral function in terms of the principal factor regulating the urine flow rate, the urethral cross-Sectional Area.
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Investigation of urethral flow and cross-Sectional Area using video-urodynamics
Proceedings of the 22nd Annual International Conference of the IEEE Engineering in Medicine and Biology Society (Cat. No.00CH37143), 1Co-Authors: Margot S. Damaser, James S. Walter, S. Rao, A. Jamnia, John S. WheelerAbstract:An accurate mathematical model predicting urethral cross-Sectional Area from urodynamic data could be useful for diagnosis of voiding dysfunction. The purpose of this project was to use fluoroscopy images of the female urethra during voiding to verify a shape assumption for the urethra and a model of laminar flow in the urethra. Maximum flow rate and simultaneous bladder and detrusor pressures during voiding were used independently in a formula based on Bernoulli's Law to predict the minimum cross-Sectional Area of the urethra. Cross-Sectional Area of the urethra was also calculated from fluoroscopic data assuming a circular cross-section. Nine adult female subjects were tested using videourodynamics. Maximum flow rate during voiding was 14.4/spl plusmn/3.0 ml/sec. Bladder, abdominal, and detrusor pressure simultaneous with maximum flow rate were 63/spl plusmn/7, 29/spl plusmn/6, and 33/spl plusmn/6 cm H/sub 2/O, respectively. The minimum cross-Sectional Area of the urethra, predicted from pressure and flow was 4.4/spl plusmn/1.0 mm/sup 2/ using bladder pressure and 6.6/spl plusmn/1.6 mm/sup 2/ using detrusor pressure. The minimum and maximum cross-Sectional Areas of the urethra from fluoroscopy data were 7.9/spl plusmn/1.9 and 93.1/spl plusmn/31.0 mm/sup 2/, respectively. Percentage error of the predictions of Area from pressure and flow were 39/spl plusmn/6% using bladder pressure and 33/spl plusmn/7% using detrusor pressure. Detrusor pressure gives a more accurate prediction of minimum cross-Sectional Area than bladder pressure, although the predictions were not significantly different. Future work will be aimed at improving the accuracy of both measurements and mathematical models.
Michael S. Cartwright - One of the best experts on this subject based on the ideXlab platform.
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Cross‐Sectional Area reference values of the median nerve at the palm using ultrasound
Muscle & nerve, 2020Co-Authors: Nikita Jain, Eduardo Cortez‐garcia, Michael S. CartwrightAbstract:BACKGROUND The most common neuromuscular ultrasound abnormality in carpal tunnel syndrome is enlargement of the median nerve near the distal wrist crease, but sometimes the median nerve enlarges in the palm, just distal to the transverse carpal ligament. This study was conducted to devise a protocol for measuring the median nerve in the palm and to generate reference values for nerve cross-Sectional Area at this site. METHODS A systematic protocol was developed, 30 healthy individuals underwent ultrasound of the median nerve in the palm bilaterally, and cross-Sectional Area was recorded. RESULTS The mean cross-Sectional Area of the median nerve at the palm was between 11.4 mm2 (95% confidence interval [CI] [10.4,12.4]) and 11.6 mm2 (95%CI [10.6,12.6]). CONCLUSIONS The median nerve can be measured just distal to the hook of the hamate in the palm, and the mean cross-Sectional Area at this site is slightly larger than it is at the distal wrist crease.
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Nerve cross-Sectional Area in extremes of age.
Muscle & nerve, 2013Co-Authors: Michael S. Cartwright, David R. Mayans, Natalie A. Gillson, Leah Griffin, Francis O. WalkerAbstract:Introduction: Nerve cross-Sectional Area reference values have been reported for many nerves, but there have been few studies in pediatric and geriatric populations. This study was conducted to determine the influence of age on nerve cross-Sectional Area. Methods: Thirty-two children (3 months to 16 years) and 20 geriatric adults (67–92 years) without known neurologic conditions underwent bilateral ultrasound to measure the Area of the following nerves: median at the wrist and forearm; ulnar at the wrist and elbow; radial in the spiral groove; sciatic in the distal thigh; fibular at the knee; tibial at the knee and ankle; and sural at the ankle. Results: In general, nerve cross-Sectional Area increased with age. Nerve size correlated most closely with age, but a correlation was also seen with body mass index. Conclusions: Nerve cross-Sectional Area increases with age, which is important to note when using ultrasound to evaluate children and geriatric patients. Muscle Nerve 47: 890–893, 2013
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Cross-Sectional Area reference values for nerve ultrasonography
Muscle & nerve, 2008Co-Authors: Michael S. Cartwright, Joon Shik Yoon, Leah Passmore, Martin E. Brown, James B. Caress, Francis O. WalkerAbstract:Ultrasound allows for a non-invasive structural assessment of nerves, muscles, and surrounding tissues, and therefore it is increasingly being used as a supplement to traditional electrodiagnostic studies. As investigators have begun to use ultrasound to explore peripheral nerves, it has become clear that conditions such as entrapment, hereditary neuropathies, acquired neuropathies, trauma, and nerve tumors result in an increase in nerve cross-Sectional Area. Reference values have not been published for the cross-Sectional Area of many nerves commonly studied in diseases of the peripheral nervous system, so our goal was to obtain reference values for the nerve cross-Sectional Area at the following sites: radial at antecubital fossa; radial at distal spiral groove; musculocutaneous in upper arm; trunks of the brachial plexus; vagus at carotid bifurcation; sciatic in distal thigh; tibial in popliteal fossa; tibial in proximal calf; tibial at ankle; peroneal in popliteal fossa; peroneal at fibular head; and sural in distal calf. Mean cross-Sectional Area, as well as side-to-side differences, are reported for each site, and qualitative data are provided to guide imaging at each site. The information provided in this study should serve as the starting point for quantitatively evaluating these nerve sites with ultrasound.
