Flexural Rigidity

This work investigates the effects of oar-shaft stiffness and length on rowing biomechanics. The mechanical properties of the oar-shafts were examined using an end-loaded cantilever system, and theoretical relations were proposed between the mechanics of the oar-shafts and rowing performance. On-water experiments were subsequently conducted and rowing biomechanics measured via the PowerLine Rowing Instrumentation System. The PowerLine system measures force and oar angle on the oarlock, as well as proper boat acceleration. The convergent validity and test-retest reliability of the PowerLine force measurements were determined prior to the on-water experiments.

Rorqual whales (Balaenopteridae) lunge at high speed with mouth open to nearly 90 degrees in order to engulf large volumes of prey-laden water. This feeding process is enabled by extremely 2 large skulls and mandibles that increase mouth area, thereby facilitating the flux of water into the mouth. When these mandibles are lowered during lunge-feeding, they are exposed to high drag and therefore may be subject to significant bending forces. We hypothesized that these mandibles exhibited a mechanical design (shape and density distribution) that enables these bones to accommodate high loads during lunge-feeding without exceeding their breaking strength. We used quantitative computed tomography (QCT) to determine the three-dimensional geometry and density distribution of a pair of sub-adult humpback whale (Megaptera novaeangliae) mandibles (length = 2.10 m). QCT data indicated highest bone density and crosssectional area, and therefore high resistance to bending and deflection, from the coronoid process to the middle of the dentary, which then decreased towards the anterior end of the mandible.

This study examines the relationships between the structure of fancy bouclé yarns and the bending stiffness of the input threads that are used to make those fancy yarns. Four fancy bouclé yarns and an extra two confirmation bouclé yarns were made to test the impact of the bending stiffness of the effect input threads. Six fancy yarns were made to test the impact of bending stiffness of the core thread on the fancy yarn structure. The structure of the fancy yarn was defined by the number of fancy profiles, the size of fancy profile, the circularity ratio of fancy profile and the shape factor of fancy yarn. It was found that increasing the value of the stiffness of the effect thread increased the size of fancy profile but decreased both the number of fancy profiles and the shape factor of fancy yarn. Those relationships were represented by regression models that were significant at α = 0.10. The deviation between the theoretical values and the real values was −14.39% and 2.07%. Furthe...

This study examines the relationships between the structure of fancy boucle´yarns and the bending stiffness of the input threads that are used to make those fancy yarns. Four fancy boucle´yarns and an extra two confirmation boucle´yarns were made to test the impact of the bending stiffness of the effect input threads. Six fancy yarns were made to test the impact of bending stiffness of the core thread on the fancy yarn structure. The structure of the fancy yarn was defined by the number of fancy profiles, the size of fancy profile, the circularity ratio of fancy profile and the shape factor of fancy yarn. It was found that increasing the value of the stiffness of the effect thread increased the size of fancy profile but decreased both the number of fancy profiles and the shape factor of fancy yarn. Those relationships were represented by regression models that were significant at a¼0.10. The deviation between the theoretical values and the real values was 14.39% and 2.07%. Further, up to a value of 8.636 g mm2, the bending stiffness of the core thread appeared not to have an effect on the structure of the fancy yarns. This study is important as it is the first that accounts statistically for the impact of bending stiffness of the input threads on the structure of the resultant fancy yarns. Therefore, it aids fancy yarn manufacturers when designing fancy yarns with predicted structures.

Mesh Multi-axial Pelvic organ prolapsed Tensile properties a b s t r a c t Clinical meshes used in pelvic organ prolapse (POP) repair are predominantly manufactured from monofilament polypropylene (PP). Complications from the use of these meshes in transvaginal kits, including mesh exposure and pain, have prompted two public health notifications by the FDA. The aim of this study was to compare several clinical PP POP meshes to new fabricated POP meshes, knitted from alternative polymers, for their mechanical properties using standard and clinically relevant multi-axial testing methods. Five new meshes were warp knitted to different architectures and weights from polyamide and polyetheretherketone monofilaments. A composite mesh of a polyamide mesh incorporating a gelatin layer was also fabricated to enable the potential delivery of cells on these meshes. Meshes were assessed for their structural characteristics and mechanical properties, using uniaxial stiffness, permanent strain, bending rigidity and multi-axial burst strength methods. Results were compared to three clinical urogynaecological polypropylene meshes: Polyforms, Gynemesh TM PS, and IntePros. New fabricated meshes were uniaxially less stiff (less than 0.24 N/mm and 1.20 N/mm in toe and linear regions, respectively) than the Gynemesh (0.48 N/ mm and 2.08 N/mm in toe and linear regions, respectively) and IntePro (0.57 N/mm in toe region) clinical meshes, with the gelatin coated PA mesh exhibiting lower permanent strain than Polyform clinical mesh (8.1% vs. 23.5%). New meshes had lower burst stiffness than Polyform (less than 16.9 N/mm for new meshes and 26.6 N/mm for Polyform). Within the new mesh prototypes, the PA meshes, either uncoated (4.7-5.7 μN m) or with gelatin coating (16.7 μN m) possessed lower bending rigidity than both Polyform and Gynemesh (46.2 μN m and 36.4 μN m, respectively). The new fabricated mesh designs were of similar architecture, but with some improved mechanical properties, compared to clinical POP meshes. Multi-axial analysis of new and clinical mesh designs provides greater discriminatory power in analysing mesh mechanical properties for clinical applications.

... Civil Engineering Department King Abdulaziz University, Jeddah, Saudi Arabia. ... The effect of concrete compressive strength, f' c , and tensile reinforcement ratio, ρ on the flexural behaviour of reinforced concrete beams has been investigated by Ashour [23]. ...

The actin regulatory protein, cofilin, promotes actin assembly dynamics by severing filaments and increasing the number of ends from which subunits add and dissociate. Recent studies provide biophysical descriptions of cooperative filament interactions in energetic, mechanical and structural terms. A one-dimensional Ising model with nearest-neighbor interactions permits thermodynamic analysis of cooperative binding and indicates that one or a few cofilin molecules can sever a filament. Binding and cooperative interactions are entropically driven. A significant fraction of the binding free energy results from the linked dissociation of filament-associated ions (polyelectrolyte effect), which modulate filament structure, stability and mechanics. The remaining binding free energy and essentially all of the cooperative free energy arise from the enhanced conformational dynamics of the cofilactin complex. Filament mechanics are modulated by cofilin such that cofilin-saturated filaments are approximately 10- to 20-fold more compliant in bending and twisting than bare filaments. Cofilin activity is well described by models in which discontinuities in topology, mechanics and conformational dynamics generate stress concentration and promote fracture at junctions of bare and decorated segments, analogous to the grain boundary fracture of crystalline materials and the thermally driven formation of shear transformation zones in colloidal glass.

Clinical meshes used in pelvic organ prolapse (POP) repair are predominantly manufactured from monofilament polypropylene (PP). Complications from the use of these meshes in transvaginal kits, including mesh exposure and pain, have prompted two public health notifications by the FDA. The aim of this study was to compare several clinical PP POP meshes to new fabricated POP meshes, knitted from alternative polymers, for their mechanical properties using standard and clinically relevant multi-axial testing methods. Five new meshes were warp knitted to different architectures and weights from polyamide and polyetheretherketone monofilaments. A composite mesh of a polyamide mesh incorporating a gelatin layer was also fabricated to enable the potential delivery of cells on these meshes. Meshes were assessed for their structural characteristics and mechanical properties, using uniaxial stiffness, permanent strain, bending rigidity and multi-axial burst strength methods. Results were compared to three clinical urogynaecological polypropylene meshes: Polyforms, Gynemesh TM PS, and IntePros. New fabricated meshes were uniaxially less stiff (less than 0.24 N/mm and 1.20 N/mm in toe and linear regions, respectively) than the Gynemesh (0.48 N/ mm and 2.08 N/mm in toe and linear regions, respectively) and IntePro (0.57 N/mm in toe region) clinical meshes, with the gelatin coated PA mesh exhibiting lower permanent strain than Polyform clinical mesh (8.1% vs. 23.5%). New meshes had lower burst stiffness than Polyform (less than 16.9 N/mm for new meshes and 26.6 N/mm for Polyform). Within the new mesh prototypes, the PA meshes, either uncoated (4.7-5.7 μN m) or with gelatin coating (16.7 μN m) possessed lower bending rigidity than both Polyform and Gynemesh (46.2 μN m and 36.4 μN m, respectively). The new fabricated mesh designs were of similar architecture, but with some improved mechanical properties, compared to clinical POP meshes. Multi-axial analysis of new and clinical mesh designs provides greater discriminatory power in analysing mesh mechanical properties for clinical applications.

To identify hybrid-specific differences in developmental response to mechanical perturbation (MP), we compared the effects of stem flexure on several morphological and mechanical properties of two Populus trichocarpa Torr. & A. Gray × P. deltoides Bartr. ex Marsh. hybrids, 47-174 and 11-11. In response to the MP treatment, both hybrids exhibited a significant increase in radial growth, especially in the direction of the MP (47-174, P = 0.0001; 11-11, P = 0.002), and a significant decrease in height to diameter growth ratio (P = 0.0001 for both hybrids), suggesting that MP-treated stems are more tapered than control stems. A direct consequence of the MP-induced increase in radial growth was a significant increase in flexural rigidity (EI, N mm 2) in stems of both hybrids (47-174, P = 0.0001; 11-11, P = 0.009). Both control and MP-treated stems of Hybrid 47-174 had significantly greater height to diameter ratios and EI values than the corresponding stems of Hybrid 11-11 (11-11 stem ratios and EI values were 85 and 76%, respectively, of those of 47-174). In Hybrid 47-174, Young's modulus of elasticity (E, N mm-2), a measure of stem flexibility, for MP-treated stems was only 80% of the control value (P = 0.0034), whereas MP had no significant effect on E of stems of Hybrid 11-11 (P = 0.2720). Differences in flexure response between the hybrids suggest that Hybrid 47-174 can produce a stem that is more tolerant of wind-induced flexure by altering both stem allometry and material properties, whereas Hybrid 11-11 relies solely on changes in stem allometry for enhanced stability under MP conditions.

This work investigates the effects of oar-shaft stiffness and length on rowing biomechanics. The mechanical properties of the oar-shafts were examined using an end-loaded cantilever system, and theoretical relations were proposed between the mechanics of the oar-shafts and rowing performance. On-water experiments were subsequently conducted and rowing biomechanics measured via the PowerLine Rowing Instrumentation System. The PowerLine system measures force and oar angle on the oarlock, as well as proper boat acceleration. The convergent validity and test-retest reliability of the PowerLine force measurements were determined prior to the on-water experiments. Thereafter, rowers were tested over a set distance using oar-shafts of different stiffness and length. There were slight differences in the biomechanics between rowing with the different oar configurations. However, the measured differences in the biomechanical parameters were on the same order of magnitude as the rower's inter-stroke inconsistencies.

A water intake basin is a buried box that functions as a water reservoir near shorelines. Number of these structures has been increased in the recent years and for a safe design, it is necessary to know their behaviour under applied loads. In addition to common dead, live and seismic loads, the bottom of such a basin is usually located below sea water level and endures uplift pressure as well as reaction of supporting soils. Uncertainty of these special loads complicates the structural response of this buried basin to the applied loads. Therefore, the unreliability in the soil parameter and in the rigidity of the basin structure is studied in this research by calculating the generated internal bending moments. Different loads and load combinations have been taken into account and finite element analysis is carried out for modelling nonlinear behaviour of different types of supporting soils. It is concluded that the geometry and flexural stiffness of the basin affects the analysis more than the soil parameters because the contribution of the soil modulus in the total stiffness of the system is negligible than the structural rigidity of the basin structure. In addition, inner walls and geometry of t he basin should be modelled in detail to obtain acceptable results.