scholarly journals Biomechanical Evaluation on the Bilateral Asymmetry of Complete Humeral Diaphysis in Chinese Archaeological Populations

Symmetry ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1843
Author(s):  
Yuhao Zhao ◽  
Mi Zhou ◽  
Haijun Li ◽  
Jianing He ◽  
Pianpian Wei ◽  
...  
Keyword(s):  
Cross Sections ◽  
Torsional Rigidity ◽  
Distribution Patterns ◽  
Group Differences ◽  
Micro Ct ◽  
Cross Sectional ◽  
Bilateral Asymmetry ◽  
Biomechanical Evaluation ◽  
The Mean ◽  
Humeral Diaphysis

Diaphyseal cross-sectional geometry (CSG) is an effective indicator of humeral bilateral asymmetry. However, previous studies primarily focused on CSG properties from limited locations to represent the overall bilateral biomechanical performance of humeral diaphysis. In this study, the complete humeral diaphyses of 40 pairs of humeri from three Chinese archaeological populations were scanned using high-resolution micro-CT, and their biomechanical asymmetries were quantified by morphometric mapping. Patterns of humeral asymmetry were compared between sub-groups defined by sex and population, and the representativeness of torsional rigidity asymmetry at the 35% and 50% cross-sections (J35 and J50 asymmetry) was testified. Inter-group differences were observed on the mean morphometric maps, but were not statistically significant. Analogous distribution patterns of highly asymmetrical regions, which correspond to major muscle attachments, were observed across nearly all the sexes and populations. The diaphyseal regions with high variability of bilateral asymmetry tended to present a low asymmetrical level. The J35 and J50 asymmetry were related to the overall humeral asymmetry, but the correlation was moderate and they could not reflect localized asymmetrical features across the diaphysis. This study suggests that the overall asymmetry pattern of humeral diaphysis is more complicated than previously revealed by individual sections.

Wear Mechanism of Ceramics and Surface Topography

1986 ◽  
Vol 108 (1) ◽  
pp. 9-15 ◽  
Author(s):  
T. Hisakado
Keyword(s):  
Cross Sections ◽  
Friction And Wear ◽  
Cross Sectional ◽  
Wear Rates ◽  
Contact Points ◽  
The Coefficient Of Friction ◽  
The Mean ◽  
New Criterion ◽  
Theoretical Results ◽  
Wear Tests

Assuming that harder asperities sliding on a flat surface were semicylindrical with the hemispherical ends, whose surface consisted of a series of spherical micro-asperities, effects of the number of contact points n, total area Sp of the cross-sections of grooves ploughed by harder asperities and depth of plastic zone on the coefficient of friction and wear for ceramics were theoretically analyzed. To verify theory, wear tests with various ceramic pins and a Si3N4 disk were carried out at a sliding speed of 1.63 m/s and under load of 0.98 N with no lubrication. The sizes of wear scratches on the worn surfaces were measured by means of a Talysurf and SEM photographs. The wear rates of the pins and Si3N4 disks increased with an increase in the mean cross-sectional area Sp/n of the scratches. This trend agreed with the theoretical results, which also showed that the Sp values were proportional to the wear rates. Theory also indicated the existence of a new criterion applicable to estimation of the wear rate.

Subperiosteal expansion and cortical remodeling of the human femur and tibia with aging

Science ◽  
1982 ◽  
Vol 217 (4563) ◽  
pp. 945-948 ◽  
Author(s):  
CB Ruff ◽  
WC Hayes
Keyword(s):  
Cross Sections ◽  
Lower Limb ◽  
Torsional Rigidity ◽  
American Southwest ◽  
Cross Sectional ◽  
Human Femur ◽  
Second Moments

Increases with aging in subperiosteal dimensions and second moments of area (measures of bending and torsional rigidity) in femoral and tibial cross sections are documented in an archeological sample from the American Southwest. Significant differences between cross-sectional sites and between sexes in the pattern of cortical remodeling with age are also present. These differences appear to be related to variations in the stress or strain levels in different regions of the femur and tibia which result from in vivo mechanical loadings of the lower limb.

scholarly journals Twist-to-bend ratio: an important selective factor for many rod-shaped biological structures

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Steve Wolff-Vorbeck ◽  
Max Langer ◽  
Olga Speck ◽  
Thomas Speck ◽  
Patrick Dondl
Keyword(s):  
Cross Sections ◽  
Phase Field ◽  
Material Properties ◽  
Flexural Rigidity ◽  
Torsional Rigidity ◽  
Cross Sectional ◽  
Deep Groove ◽  
Biological Structures ◽  
The Cross ◽  
Sectional Shape

AbstractMechanical optimisation plays a key role in living beings either as an immediate response of individuals or as an evolutionary adaptation of populations to changing environmental conditions. Since biological structures are the result of multifunctional evolutionary constraints, the dimensionless twist-to-bend ratio is particularly meaningful because it provides information about the ratio of flexural rigidity to torsional rigidity determined by both material properties (bending and shear modulus) and morphometric parameters (axial and polar second moment of area). The determination of the mutual contributions of material properties and structural arrangements (geometry) or their ontogenetic alteration to the overall mechanical functionality of biological structures is difficult. Numerical methods in the form of gradient flows of phase field functionals offer a means of addressing this question and of analysing the influence of the cross-sectional shape of the main load-bearing structures on the mechanical functionality. Three phase field simulations were carried out showing good agreement with the cross-sections found in selected plants: (i) U-shaped cross-sections comparable with those of Musa sp. petioles, (ii) star-shaped cross-sections with deep grooves as can be found in the lianoid wood of Condylocarpon guianense stems, and (iii) flat elliptic cross-sections with one deep groove comparable with the cross-sections of the climbing ribbon-shaped stems of Bauhinia guianensis.

A Theoretical Derivation of the Similarity of Dynamic Compaction Processes of Powder Media in Dies

1986 ◽  
Vol 108 (2) ◽  
pp. 147-152
Author(s):  
Yukio Sano
Keyword(s):  
Cross Sections ◽  
Dynamic Compaction ◽  
Simple Type ◽  
Theoretical Derivation ◽  
Cross Sectional ◽  
Density Distributions ◽  
Powder Medium ◽  
Compaction Energy ◽  
The Mean ◽  
Compaction Processes

Multiple shock compactions of powder media within a die with a rigid punch are theoretically investigated. First, similarity of dynamic compaction processes for a powder medium of a simple type is exhibited through nondimensionalized one-dimensional equations. The similarity is established after determination of three parameters, i.e., the ratio S* of the lateral surface to the cross-sectional area of the medium, the ratio M* of the mass of the punch to that of the powder medium filled in the die, and the compaction energy per unit powder volume e. The similarity indicates that the particle velocity, specific volume and pressure have the same variation with respect to nondimensional time at all points in the medium with various cross-sections and initial lengths so long as S* is kept fixed at a certain value, i.e., at the same proportional nondimensional point in the medium. The density distributions of the green compacts are necessarily identical, and so is the mean density in all compactions. Second, it is shown in one of the nondimensionalized equations that wall frictional influence in a compaction where S* → 0 is not present, while the wall frictional influence is extremely large when S* is very large, which implies that the mean densities of the compacts are larger in compactions with smaller S*. Two types of compactions can be obtained for any powder medium because the equation used is applicable to any medium.

scholarly journals Saint-Venant’s torsion of thin-walled nonhomogeneous open elliptical cross section

2021 ◽  
Vol 11 (5) ◽  
pp. 151-158
Author(s):  
István Ecsedi ◽  
Ákos József Lengyel ◽  
Attila Baksa ◽  
Dávid Gönczi
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Torsional Rigidity ◽  
Elliptical Cross Section ◽  
Curvilinear Coordinates ◽  
Torsion Problem ◽  
Cross Sectional ◽  
Elliptical Cross ◽  
Thin Walled ◽  
The One

This paper deals with the Saint-Venant’s torsion of thin-walled isotropic nonhomogeneous open elliptical cross section whose shear modulus depends on the one of the curvilinear coordinates which define the cross-sectional area of the beam. The approximate solution of torsion problem is obtained by variational method. The usual simplification assumptions are used to solve the uniform torsion problem of bars with thin-walled elliptical cross-sections. An example illustrates the application of the derived formulae of shearing stress and torsional rigidity.

Finding Echoes: An Exploration of Empathy Among Physiotherapists and Physiotherapy Students in Singapore

2021 ◽  
pp. 201010582110485
Author(s):  
Elsie Kim Hiok Lim ◽  
Gordon Jian Ting Loh ◽  
Ren Yong Ong ◽  
Rachel Ruizhen Tan ◽  
Clement Chee Kin Yan ◽  
...  
Keyword(s):  
Healthcare Workers ◽  
Healthcare Professionals ◽  
Health Professions ◽  
Group Differences ◽  
Cross Sectional Survey ◽  
Cross Sectional ◽  
Clinical Empathy ◽  
The Mean ◽  
Convenience Sampling ◽  
Physiotherapy Students

Background Empathy is an essential antecedent in motivating healthcare professionals to treat and care for their patients with compassion – few studies had explored empathy on healthcare workers. Currently, no data reported empathy amongst physiotherapists and physiotherapy students in Singapore. Objectives This study aims to: 1) measure and explore within- and between-group differences in empathy scores amongst physiotherapists and physiotherapy students in Singapore, and 2) compare the results with similar studies locally and overseas. Methods This cross-sectional survey recruited 187 participants (37 physiotherapists and 150 physiotherapy students) via convenience sampling. Participants completed the Jefferson Scale of Empathy (JSE) Health Professions (JSE-HP) and the JSE-Health Professions Students (JSE-HPS), correspondingly. The 20-item JSE-HP and JSE-HPS are validated self-reported questionnaires that measure clinical empathy using a 7-point Likert scale. Summed scores range from 20 to 140, with higher scores suggesting a higher level of empathy. Statistical analysis included descriptive statistics, independent-sample t-tests and one-way analyses of variance. Results The mean score of JSE-HP and JSE-HPS was 110.89±11.37 and 112.43±10.73, respectively. No statistically significant differences found between gender, physiotherapists and physiotherapy students, and years of study. However, physiotherapists scored significantly higher [5.08±1.24 (95% CI 4.67–5.49) vs 4.01±1.36 (95% CI 3.79–4.23), p < .001 ] in the JSE components ‘Walking in Patient's Shoes’. Conclusion Physiotherapists and physiotherapy students in Singapore have similar empathy scores to their counterparts locally and internationally. No statistically significant differences in empathy scores were found. However, physiotherapy students were less able to understand patients' perspectives. This warrants further exploration in developing this vital attribute amongst students.

Transport theory in anisotropic media

1978 ◽  
Vol 84 (3) ◽  
pp. 549-567 ◽  
Author(s):  
M. M. R. Williams
Keyword(s):  
Cross Sections ◽  
Transport Theory ◽  
Boltzmann Transport Equation ◽  
Anisotropic Media ◽  
Particle Scattering ◽  
Boltzmann Transport ◽  
Cross Sectional ◽  
Cross Sectional Dependence ◽  
Fixed Axis ◽  
The Mean

AbstractWe develop a theory of particle scattering in anisotropic media. That is, a medium in which the microstructure causes the mean free paths of the particles to become dependent on their direction of motion with respect to some fixed axis. The equation which results is similar to the normal, one-speed Boltzmann transport equation but has cross-sections which are functions of direction. This equation is solved for arbitrary cross-sectional dependence on direction in plane geometry.

scholarly journals AB0667 ACHILLES PAIN PERSISTENCE IN PATIENTS AFFECTED BY SPONDYLOARTHRITIS: ULTRASONOGRAPHIC AND BIOMECHANICAL STUDY.

2020 ◽  
Vol 79 (Suppl 1) ◽  
pp. 1628.2-1629
Author(s):  
A. Batticciotto ◽  
S. Olivieri ◽  
R. Talotta ◽  
A. Cappelli ◽  
A. Preda ◽  
...  
Keyword(s):  
Functional Disability ◽  
Power Doppler ◽  
Biomechanical Study ◽  
Ankle Dorsiflexion ◽  
Control Group ◽  
Cross Sectional ◽  
Ultrasound Study ◽  
Number Of Patients ◽  
Biomechanical Evaluation ◽  
The Mean

Background:Enthesis anatomy and biomechanics have a key role in Spondyloarthritis (SpA) pathogenesis (1) but few data are available about the influence of structural and biomechanical changes of Achilles tendon (AT) on persisting pain in longstanding SpA patients.Objectives:To correlate AT pain in longstanding SpA patients with ultrasonographic detectable disorders and biomechanical abnormalities.Methods:We performed a monocentric cross-sectional analysis including 35 consecutive patients affected by SpA (13 with Psoriatic Arthritis, 9 with Enteropathic SpA, 6 with Ankylosing Spondylitis and 7 with Undifferentiated SpA) under treatment with anti- TNF agents. A rheumatologic clinical and clinimetric evaluation (AT VAS pain, BASDAI, BASFI, HAQ), an ultrasound study of AT according to the Madrid Sonographic Enthesis Index (MASEI) score and a podiatrist biomechanical evaluation [Foot posture index (FPI), degree of ankle dorsiflexion with the knee extended and flexed] were performed.Results:Study population (13 F; 22 M; mean age 54.9 ±13.9 years; mean disease duration 9.5 ± 5.0 years; mean BMI 25.8 ±4.4) showed a mean AT VAS pain of 3.4 ± 2.2, a mean HAQ of 0.6 ± 0.6, a mean BASDAI of 3.3 ±2.1 and a mean BASFI of 2.2 ±1.9. At the ultrasonographic evaluation 47% (33/70) of the AT entheses analysed presented a dishomogeneous echostructure, 31% (22/70) structural thickness, 53% (37/70) calcifications, 10% (7/70) erosions, 44% (31/70) a retrocalcanear bursitis. A power Doppler positivity was found only in 0.07% (5/70) of the AT.At the biomechanical evaluation 50% (35/70) of the feet showed a FPI score between 0 and + 5 (neutral foot), 46% (32/70) a FPI score between +6 and +9 (slight foot pronation) and 6% (4/70) a FPI score between -1 and -4 (slight foot supination).The mean degree of ankle dorsiflexion with extended knee was 8.4 ± 3.9 with the 61% (43/70) of the patients with a maximum dorsiflexion < 10° of whom 46% (20/43) do not recover after the knee flexion.We found a between the mean degree of left ankle dorsiflexion with extended/flexed knee both with ultrasound-revealed left AT enthesis calcifications (p=0.014/0.037) and with left AT enthesis thickness (p=0.049/0.035), and a significant association between the mean degree of right ankle dorsiflexion and extended/flexed knee and ultrasound-revealed right AT calcifications (p=0.008/0.012). Moreover, we noticed an inverse correlation between the mean overall degree of ankle dorsiflexion with extended/flexed knee and the BASFI values (p=0.007/0.004). AT VAS pain was statistically related with Achilles PDUS signal persistence (p=0.048) but not with US signs of chronic entesopathy or biomechanical alterations [calcification (p=0.39), erosions (p=0.74)]. The limits of the study were the low number of patients recruited and the lack of a control group.Conclusion:In this monocentric study on a cohort of SpA patients, we demonstrated a statistically significant correlation between ankle–subtalar joint complex biomechanics alterations, ultrasonographic signs of chronic enthesopathy and clinimetric index of functional disability. Residual Achilles pain seems to be related to US signs of active enthesitis.References:[1]The enthesis organ concept and its relevance to the spondyloarthropathies. Benjamin, M and McGonagle, D. s.l.: Adv Exp Med Biol, 2009, Vol. 649.[2]The Synovio-entheseal Complex and Its Role in Tendon and Capsular Associated Inflammation. McGonagle, E D, Aydin, SZ and Tan, AL. 0, s.l.: J Rheumatol Suppl, 2012, Vol. 89Disclosure of Interests:None declared

Aerodynamic behavior of wind turbines with polygonal cross- sectional tower

2021 ◽  
Author(s):  
Yong Chul Kim ◽  
Yukio Tamura
Keyword(s):  
Cross Section ◽  
Wind Turbines ◽  
Cross Sections ◽  
Lift Force ◽  
Circular Cross Section ◽  
Force Coefficient ◽  
Cross Sectional ◽  
The World ◽  
The Mean ◽  
Power Generation Systems

<p>Wind turbines are commonly used power generation systems around the world and their application is becoming increasingly widespread. Traditionally, circular‐cross‐section wind towers have been used, but recent upsizing of wind turbines has exposed weaknesses of these structures, including problems related to manufacturing and inadequate strength. Thus, the concept of site‐ assembled modular towers with polygonal cross‐sections such as octagonal and/or tetradecagonal has been proposed, but their wind‐resistant performances have not been clearly investigated. In the present study, the wind‐resistant performances of polygonal cross‐sectional towers were investigated through wind tunnel tests. It was thus found that the maximum force coefficient of the upper structure is larger than that of the tower, which makes the effect of cross‐sectional tower shape rather small. The mean and fluctuating lift force coefficients of a helical square cross‐sectional tower were quite small for cases of tower only and wind turbine.</p>

scholarly journals Biomechanical Evaluation Comparing Pulvertaft Weave and Side-to-Side Tenorrhaphy Using Porcine Tendons

2020 ◽  
Vol 25 (04) ◽  
pp. 447-452
Author(s):  
Soha Sajid ◽  
Emily Day ◽  
Jan Herman Kuiper ◽  
Rohit Singh ◽  
Simon Pickard
Keyword(s):  
Cyclic Loading ◽  
Creep Rate ◽  
Cyclic Creep ◽  
Cross Sectional ◽  
Load To Failure ◽  
Cyclical Loading ◽  
Biomechanical Evaluation ◽  
The Mean ◽  
Flexor Digitorum ◽  
Permanent Elongation

Background: Pulvertaft Weave (PTW) is an established method of tenorrhapy in tendon transfers. Previous studies have suggested that a Side-to-Side (STS) tenorrhapy is easier to perform has the same advantages and has greater load to failure, ultimate load and stiffness compared to PTW. However, there is insufficient data comparing behaviour of STS and PTW during cyclical loading. The aim of this study is to compare these two methods in terms of creep after cyclic landing. Methods: Fresh porcine flexor digitorum tendons were used. Ten tendon PTW and ten STS repairs were performed. Cross sectional diameter was measured. The tendon repairs were tested by applying tension up to 25N for 100 cycles, followed by tension up to 75N for 100 cycles, followed by loading to failure. Force-displacement data was used to determine the creep of the repaired tendon. Results: All tendons survived 100 cycles of loading at 25N. After 1 cycle of loading, the mean cyclic creep in the PTW group was almost 3 mm larger than in the STS group (p = 0.046). After 100 cycles, the mean cyclic creep in the PTW group was 4.4 mm larger (p = 0.008). The cyclic creep rate was significantly larger in the PTW group (p < 0.001). All STS but only four PTW repairs survived after cyclic loading at 75N (p = 0.01). After 1 cycle and 100 cycles, mean creep of the surviving PTW samples was almost 7 mm (p = 0.006) and almost 9 mm (p = 0.004) larger than the STS group. The mean load to failure was four times larger in the STS group than the PTW group (p = 0.004). Conclusions: STS repairs have a significantly smaller permanent elongation after cyclic loading at 25N and 75N, a significantly smaller cyclic creep rate, require a significantly larger load to fail. This implies that STS repairs are less likely to elongate after cyclic loading and can withstand greater loads. These properties can be valuable in allowing patients to commence mobilisation immediately after surgery.

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