Curvature Of Shaft Research Articles

Femora from an exceptionally large population of coeval ornithomimosaurs yield evidence of sexual dimorphism in extinct theropod dinosaurs.

Sexual dimorphism is challenging to detect among fossils due to a lack of statistical representativeness. The Angeac-Charente Lagerstätte (France) represents a remarkable 'snapshot' from a Berriasian (Early Cretaceous) ecosystem and offers a unique opportunity to study intraspecific variation among a herd of at least 61 coeval ornithomimosaurs. Herein, we investigated the hindlimb variation across the best-preserved specimens from the herd through 3D Geometric Morphometrics and Gaussian Mixture Modeling. Our results based on complete and fragmented femora evidenced a dimorphism characterized by variations in the shaft curvature and the distal epiphysis width. Since the same features vary between sexes among modern avian dinosaurs, crocodilians, and more distant amniotes, we attributed this bimodal variation to sexual dimorphism based on the extant phylogenetic bracketing approach. Documenting sexual dimorphism in fossil dinosaurs allows a better characterization and accounting of intraspecific variations, which is particularly relevant to address ongoing taxonomical and ecological questions relative to dinosaur evolution.

Geometric variation of the human tibia-fibula: a public dataset of tibia-fibula surface meshes and statistical shape model.

Variation in tibia geometry is a risk factor for tibial stress fractures. Geometric variability in bones is often quantified using statistical shape modelling. Statistical shape models (SSM) offer a method to assess three-dimensional variation of structures and identify the source of variation. Although SSM have been used widely to assess long bones, there is limited open-source datasets of this kind. Overall, the creation of SSM can be an expensive process, that requires advanced skills. A publicly available tibia shape model would be beneficial as it enables researchers to improve skills. Further, it could benefit health, sport and medicine with the potential to assess geometries suitable for medical equipment, and aid in clinical diagnosis. This study aimed to: (i) quantify tibial geometry using a SSM; and (ii) provide the SSM and associated code as an open-source dataset. Lower limb computed tomography (CT) scans from the right tibia-fibula of 30 cadavers (male n = 20, female n = 10) were obtained from the New Mexico Decedent Image Database. Tibias were segmented and reconstructed into both cortical and trabecular sections. Fibulas were segmented as a singular surface. The segmented bones were used to develop three SSM of the: (i) tibia; (ii) tibia-fibula; and (iii) cortical-trabecular. Principal component analysis was applied to obtain the three SSM, with the principal components that explained 95% of geometric variation retained. Overall size was the main source of variation in all three models accounting for 90.31%, 84.24% and 85.06%. Other sources of geometric variation in the tibia surface models included overall and midshaft thickness; prominence and size of the condyle plateau, tibial tuberosity, and anterior crest; and axial torsion of the tibial shaft. Further variations in the tibia-fibula model included midshaft thickness of the fibula; fibula head position relative to the tibia; tibia and fibula anterior-posterior curvature; fibula posterior curvature; tibia plateau rotation; and interosseous width. The main sources of variation in the cortical-trabecular model other than general size included variation in the medulla cavity diameter; cortical thickness; anterior-posterior shaft curvature; and the volume of trabecular bone in the proximal and distal ends of the bone. Variations that could increase the risk of tibial stress injury were observed, these included general tibial thickness, midshaft thickness, tibial length and medulla cavity diameter (indicative of cortical thickness). Further research is needed to better understand the effect of these tibial-fibula shape characteristics on tibial stress and injury risk. This SSM, the associated code, and three use examples for the SSM have been provided in an open-source dataset. The developed tibial surface models and statistical shape model will be made available for use at: https://simtk.org/projects/ssm_tibia.

Motion Measurement and Analysis of Different Instruments for Single-Incision Laparoscopic Surgery.

Objective To objectively compare and analyze the range of motion of three types of instruments for single-incision laparoscopic surgery. Material and Methods. Ten experienced participants were recruited. Straight instruments (Group A), straight/articulating instruments (Group B), and precurved instruments (Group C) were used to complete the transferring task through one site in a laparoscopic simulator. Straight instruments via two separate sites (Group D) served as control. The operation time of each group was recorded. Instrument positions were measured by an optical tracking system. The inserted length and pivoting angles were derived via MATLAB. Results There was a significant difference in operation time between groups (D < A < B < C, p < 0.01). The range of motion of instruments was different on instrument types and surgical approaches. A significant difference in the inserted length was found between groups. Instrument conflicts and inadequate triangulation were found in Group A; instrument conflicts were found in Group B; no obvious conflicts and triangulation problems were observed in Group C. The operation in Group C was similar to the operation in Group D but differed on the left/right pivoting angles. Conclusion Different types of instruments have different ranges of motion in single-incision laparoscopic surgery. Working with precurved instruments seems like a compromise to traditional laparoscopic surgery if the transmission property, and shaft curvature of the instruments could be improved. An integrated mechanical platform or robotic system might be the ultimate solution for single-incision laparoscopic surgery to pursue even less trauma.

Stability analysis of rotating shaft under electromagnetic and bearing oil-film forces

The stability of the fixed pints of a flexible rotor supported by journal bearings is investigated through the Bifurcation diagrams. In this paper the effect of nonlinear electromagnetic harmonic force is added to the simultaneous consideration of the effects of the nonlinearity in curvature and inertia, mass eccentricity and hydrodynamic forces of the journal bearings. Solution of the Reynolds equation renders the pressure distribution in the bearings. The bearing forces are found from integrating the pressure distribution on the surface of bearings. Derivation of the equations is performed using the Hamilton's principle and the nonlinearity terms are related to the eccentricity and the curvature of shaft. Primary and combination resonances are imposed to the rotor-bearing system and steady state responses show the effects of magnetic and bearing forces on the stability of amplitudes. In combination resonance, frequency of the electromagnetic load is tuned as the average of the forward and backward natural frequencies of the rotor. Existence of unstable Hopf points demonstrates that periodic, quasi-periodic and chaotic motions may be arisen in the nonlinear behavior of rotor.

Study on the friction resistance calculation method of a flexible shaft of wire rope based on genetic algorithm

This study aims to finding out the calculation formula of friction resistance of steel wire's flexible shaft in bending push-pull state. The operation principle is based on the adhesive friction theory and Newton's classical friction formula. The friction force f is measured by experiment under the conditions of same length L, different diameter D and different curvature K, and the curve trajectory equation is obtained by curve fitting with mathematical tools. Then, according to the experimental data, the greater the curvature of flexible shaft is (that's, the smaller the bending radius is), the greater the positive pressure between shaft core and the sheath will be. The positive pressure N between the shaft core and the sheath is equal to the curvature K direct ratio. Therefore, it can be concluded that the positive pressure N of the shaft core and sheath is proportional to the curvature K, and the proportional coefficient β is introduced. The experimental results show that the functional relationship between the friction force F and the curvature K of the flexible shaft can be derived, the diameter D and curvature K of the mandrel have a great influence on the friction resistance of the flexible shaft, that is, the empirical friction resistance formula. In order to reduce the relative error and improve the accuracy of the formula. By combining elite retention strategy with roulette method and replacing the current worst genetic algorithm with historical optimum, the parameter β in the formula is optimized. After optimization, the calculation formula of friction resistance of four flexible shafts of steel wire under bending push-pull state is obtained. The author's pioneer work has contributed to the calculation of friction resistance under bending push-pull, and the average calculation error is 5%, which meets the requirements of calculation accuracy.

ESM-CT: a precise method for localization of DBS electrodes in CT images

BackgroundDeep brain stimulation (DBS) of the subthalamic nucleus produces variable effects in Parkinson disease. Variation may result from different electrode positions relative to target. Thus, precise electrode localization is crucial when investigating DBS effects. New methodWe developed a semi-automated method, Electrode Shaft Modeling in CT images (ESM-CT) to reconstruct DBS lead trajectories and contact locations. We evaluated methodological sensitivity to operator-dependent steps, robustness to image resampling, and test-retest replicability. ESM-CT was applied in 56 patients to study electrode position change (and relation to time between scans, postoperative subdural air volume, and head tilt during acquisition) between images acquired immediately post-implantation (DBS-CT) and months later (DEL-CT). ResultsElectrode tip localization was robust to image resampling and replicable to within ∼ 0.2 mm on test-retest comparisons. Systematic electrode displacement occurred rostral-ventral-lateral between DBS-CT and DEL-CT scans. Head angle was a major explanatory factor (p < 0.001,Pearson’s r = 0.46, both sides) and volume of subdural air weakly predicted electrode displacement (p = 0.02,r = 0.29:p = 0.1,r = 0.25 for left:right). Modeled shaft curvature was slightly greater in DEL-CT. Magnitude of displacement and degree of curvature were independent of elapsed time between scans. Comparison with Existing MethodsComparison of ESM-CT against two existing methods revealed systematic differences in one coordinate (1 ± 0.3 mm,p < 0.001) for one method and in three coordinates for another method (x:0.1 ± 0.1 mm, y:0.4 ± 0.2 mm, z:0.4 ± 0.2 mm, p < 10−10). Within-method coordinate variability across participants is similar. ConclusionWe describe a robust and precise method for CT DBS contact localization. Application revealed that acquisition head angle significantly impacts electrode position. DBS localization schemes should account for head angle.

Causes and Consequences of Tool Shape Variation in New Caledonian Crows

Hominins have been making tools for over three million years [1], yet the earliest known hooked tools appeared as recently as 90,000 years ago [2]. Hook innovation is likely to have boosted our ancestors' hunting and fishing efficiency [3], marking a major transition in human technological evolution. The New Caledonian crow is the only non-human animal known to craft hooks in the wild [4, 5]. Crows manufacture hooked stick tools in a multi-stage process, involving the detachment of a branch from suitable vegetation; "sculpting" of a terminal hook from the nodal joint; and often additional adjustments, such as length trimming, shaft bending, and bark stripping [4, 6, 7]. Although tools made by a given population share key design features [4, 6, 8], they vary appreciably in overall shape and hook dimensions. Using wild-caught, temporarily captive crows, we experimentally investigated causes and consequences of variation in hook-tool morphology. We found that bird age, manufacture method, and raw-material properties influenced tool morphology, and that hook geometry in turn affected crows' foraging efficiency. Specifically, hook depth varied with both detachment technique and plant rigidity, and deeper hooks enabled faster prey extraction in the provided tasks. Older crows manufactured tools of distinctive shape, with pronounced shaft curvature and hooks of intermediate depth. Future work should explore the interactive effects of extrinsic and intrinsic factors on tool production and deployment. Our study provides a quantitative assessment of the drivers and functional significance of tool shape variation in a non-human animal, affording valuable comparative insights into early hominin tool crafting [9].

Three-dimensional assessment of curvature, torsion, and canal flare index of the humerus of skeletally mature nonchondrodystrophic dogs.

OBJECTIVE To assess 3-D geometry of the humerus of dogs and determine whether the craniocaudal canal flare index (CFI) is associated with specific geometric features. SAMPLE CT images (n = 40) and radiographs (38) for 2 groups of skeletally mature nonchondrodystrophic dogs. PROCEDURES General dimensions (length, CFI, cortical thickness, and humeral head offset), curvature (shaft, humeral head, and glenoid cavity), version (humeral head and greater tubercle), and torsion were evaluated on CT images. Dogs were allocated into 3 groups on the basis of the craniocaudal CFI, and results were compared among these 3 groups. The CT measurements were compared with radiographic measurements obtained for another group of dogs. RESULTS Mean ± SD humeral head version was -75.9 ± 9.6° (range, -100.7° to -59.4°). Mean mechanical lateral distal humeral angle, mechanical caudal proximal humeral angle, and mechanical cranial distal humeral angle were 89.5 ± 3.5°, 50.2 ± 4.5°, and 72.9 ± 7.8°, respectively, and did not differ from corresponding radiographic measurements. Mean humeral curvature was 20.4 ± 4.4° (range, 9.6° to 30.5°). Mean craniocaudal CFI was 1.74 ± 0.18 (range, 1.37 to 2.10). Dogs with a high craniocaudal CFI had thicker cranial and medial cortices than dogs with a low craniocaudal CFI. Increased body weight was associated with a lower craniocaudal CFI. Radiographic and CT measurements of craniocaudal CFI and curvature differed significantly. CONCLUSIONS AND CLINICAL RELEVANCE CT-based 3-D reconstructions allowed the assessment of shaft angulation, torsion, and CFI. Radiographic and CT measurements of shaft curvature and CFI may differ.

The role of tunica vaginalis flap in staged repair of hypospadias

ObjectiveThe surgical repair of hypospadias is done in two stages in a select group of patients with severe anomaly. The first stage (I) procedure consists of correction of penile shaft curvature and second stage (II) repair involves the creation of a neourethra. This neourethra needs a cover of an intermediate layer in order to have good functional and cosmetic results. Among the various local flaps, tunica vaginalis flap is a good option for the use as an intermediate layer. MethodsWe have managed 22 patients of chordee with hypospadias by staged repair. In Stage I, chordee correction was done by dividing the urethral plate and covering the penile shaft with dorsal prepucial flaps. In Stage II, a neourethra was created and covered with tunica vaginalis flap either through the same incision (14/22) or via a subcutaneous tunnel (8/22). An indwelling catheter was kept for 10 to 12 days. ResultsEighteen (81.8%) patients had successful functional and cosmetic repair. Two patients (9.1%) had urethrocutaneous fistula of which one healed on subsequent dilatation while the other one (4.5%) needed repair. Overall fistula formation rate was 4.5%. In two patients, the external urinary meatus could be made upto subglanular or coronal level. ConclusionStaged repair of chordee with hypospadias is valuable in selected group of patients and tunica vaginalis flap is an excellent intermediate layer to cover the neourethra. However preoperative counseling is particularly essential in patients where the external urinary meatus can be created at coronal or subglanular level.

Influence of chondrodystrophy and brachycephaly on geometry of the humerus in dogs.

To assess the geometry of canine humeri as seen on radiographs in chondrodystrophic dogs (CD) and brachycephalic dogs (BD) compared to non-chondrodystrophic dogs (NCD). Mediolateral (ML) and craniocaudal (CC) radiographs of skeletally mature humeri were used (CD [n = 5], BD [n = 9], NCD [n = 48]) to evaluate general dimensions (length, width, canal flare, cortical thickness), curvature (shaft, humeral head, and glenoid), and angulation (humeral head and condyle). Measurements from CD, BD, and NCD were compared. Mean humeral length was shorter in CD (108 mm) compared to BD (184 mm, p = 0.001) and NCD (183 mm, p <0.001). Craniocaudal cortical thickness at 70% of humeral length and ML cortical thickness at 30%, 50%, and 70% of humeral length were less in CD compared to BD and NCD. Humeral shaft curvature was greater in CD (9.9°) compared to BD (6.7°, p = 0.023). The ratio of glenoid radius of curvature / humeral length was greater for CD (11.1%) compared to NCD (9.7%, p = 0.013). The ratio of humeral width / humeral length was greater for BD (29.4%) compared to NCD (26.2%, p = 0.043). The ratio of glenoid length / humeral length was greater in CD (18.0%) than BD (16.4%, p = 0.048) and NCD (15.6%, p <0.001). Bone proportions and curvature in CD differ from BD and NCD. Differences are minor and unlikely to have clinical significance.

Further analysis of the Glans-Urethral Meatus-Shaft (GMS) hypospadias score: Correlation with postoperative complications

The Glans-Urethral Meatus-Shaft (GMS) score is a concise and reproducible way to describe hypospadias severity. We classified boys undergoing primary hypospadias repair to determine the correlation between GMS score and postoperative complications. Between February 2011 and August 2013, patients undergoing primary hypospadias repair were prospectively scored using the GMS classification. GMS scoring included a 1-4 scale for each component: G - glans size/urethral plate quality, M - meatal location, and S - degree of shaft curvature, with more unfavorable characteristics assigned higher scores [Figure]. Demographics, repair type, and complications (urethrocutaneous fistula, meatal stenosis, glans dehiscence, phimosis, recurrent chordee and stricture) were assessed. Total and individual component scores were tested in uni- and multivariate analysis. Two-hundred and sixty-two boys (mean age 12.3 ± 13.7 months) undergoing primary hypospadias repair had a GMS score assigned. Mean GMS score was 7 ± 2.5 (G 2.1 ± 0.9, M 2.4 ± 1, S 2.4 ± 1). Mean clinical follow-up was 17.7 ± 9.3 months. Thirty-seven children (14.1%) had 45 complications. A significant relationship between the total GMS score and presence of any complication (p < 0.001) was observed; for every unit increase in GMS score the odds of any postoperative complication increased 1.44 times (95% CI, 1.24-1.68). Urethrocutaneuous fistula was the most common complication, occurring in 21 of 239 (8.8%) of single-stage repairs. Patients with mild hypospadias (GMS 3-6) had a 2.4% fistula rate vs. 11.1% for moderate (GMS 7-9) and 22.6% for severe (GMS 10-12) hypospadias (p < 0.001). Degree of chordee was an independent predictor of fistula on multivariate analysis; S4 (>60° ventral curvature) patients were 27 times more likely to develop a fistula than S1 (no curvature) boys (95% CI, 3.2-229). The GMS score is based on anatomic features (i.e. glans size/urethral plate quality, location of meatus, and degree of chordee) felt to most likely impact functional and cosmetic outcomes following hypospadias repair. We demonstrated a statistically significant increase in the likelihood of any postoperative complication with every unit increase in total GMS score. The concept that factors aside from meatal location affect hypospadias repair and outcomes is not novel, and degree of ventral curvature and urethral plate quality are often cited as important factors. In our series, boys with greater than 60° of ventral curvature undergoing a single-stage repair were 27 times more likely to develop a fistula than those without chordee on multivariate analysis, making severe curvature an independent predictor of urethrocutaneous fistula formation. That meatal location did not retain significance on multivariate analysis highlights the importance of considering the entire hypospadias complex when determining severity, rather than just evaluating the position of the meatus. Our study has several limitations that warrant consideration. While GMS scores were assigned prospectively, the data was collected retrospectively, subjecting it to flaws inherent with such study design. Furthermore, type of repair is influenced by surgeon preference and subjective assessment of hypospadias characteristics not incorporated in our scoring system (i.e. tissue quality, urethral hypoplasia, penoscrotal transposition). Despite these limitations, our study demonstrates a strong correlation between the GMS classification and surgical complications, furthering supporting its potential as a tool to standardize hypospadias severity and gauge postoperative complications. The Glans-Urethral Meatus-Shaft (GMS) classification provides a means by which hypospadias severity and reporting can be standardized, which may improve inter-study comparison of reconstructive outcomes. There is a strong correlation between complication risk and total GMS score. Degree of chordee (S score) is independently predictive of fistula rate.

Modeling and estimation of tip contact force for steerable ablation catheters.

The efficacy of catheter-based cardiac ablation procedures can be significantly improved if real-time information is available concerning contact forces between the catheter tip and cardiac tissue. However, the widely used ablation catheters are not equipped for force sensing. This paper proposes a technique for estimating the contact forces without direct force measurements by studying the changes in the shape of the deflectable distal section of a conventional 7-Fr catheter (henceforth called the "deflectable distal shaft," the "deflectable shaft," or the "shaft" of the catheter) in different loading situations. First, the shaft curvature when the tip is moving in free space is studied and based on that, a kinematic model for the deflectable shaft in free space is proposed. In the next step, the shaft shape is analyzed in the case where the tip is in contact with the environment, and it is shown that the curvature of the deflectable shaft provides useful information about the loading status of the catheter and can be used to define an index for determining the range of contact forces exerted by the ablation tip. Experiments with two different steerable ablation catheters show that the defined index can detect the range of applied contact forces correctly in more than 80% of the cases. Based on the proposed technique, a framework for obtaining contact force information by using the shaft curvature at a limited number of points along the deflectable shaft is constructed. The proposed kinematic model and the force estimation technique can be implemented together to describe the catheter's behavior before contact, detect tip/tissue contact, and determine the range of contact forces. This study proves that the flexibility of the catheter's distal shaft provides a means of estimating the force exerted on tissue by the ablation tip.

Radiographic study of the fifth metatarsal for optimal intramedullary screw fixation of Jones fracture.

Jones fractures occur in the relatively avascular metadiaphyseal junction of the fifth metatarsal (MT), which predisposes these fractures to delayed union and nonunion. Operative treatment with intramedullary (IM) screw fixation is recommended in certain cases. Incorrect screw selection can lead to refractures, nonunion, and cortical blowout fractures. A better understanding of the anatomy of the fifth MT could aid in preoperative planning, guide screw size selection, and minimize complications. We retrospectively identified foot computed tomographic (CT) scans of 119 patients that met inclusion criteria. Using interactive 3-dimensional (3-D) models, the following measurements were calculated: MT length, "straight segment length" (distance from the base of the MT to the shaft curvature), and canal diameter. The diaphysis had a lateroplantar curvature where the medullary canal began to taper. The average straight segment length was 52 mm, and corresponded to 68% of the overall length of the MT from its proximal end. The medullary canal cross-section was elliptical rather than circular, with widest width in the sagittal plane and narrowest in coronal plane. The average coronal canal diameter at the isthmus was 5.0 mm. A coronal diameter greater than 4.5 mm at the isthmus was present in 81% of males and 74% of females. To our knowledge, this is the first anatomic description of the fifth metatarsal based on 3-D imaging. Excessive screw length could be avoided by keeping screw length less than 68% of the length of the fifth metatarsal. A greater than 4.5 mm diameter screw might be needed to provide adequate fixation for most study patients since the isthmus of the medullary canal for most were greater than 4.5 mm. Our results provide an improved understanding of the fifth metatarsal anatomy to guide screw diameter and length selection to maximize screw fixation and minimize complications.

A new method of measuring frontal plane femoral shaft curvature provides preliminary data on an association between femoral shape, weight, and the difference between anatomic and mechanical alignment in knees with, or at risk of developing osteoarthritis

s / Osteoarthritis and Cartilage 22 (2014) S57–S489 S212 371 A NEW METHOD OF MEASURING FRONTAL PLANE FEMORAL SHAFT CURVATURE PROVIDES PRELIMINARY DATA ON AN ASSOCIATION BETWEEN FEMORAL SHAPE, WEIGHT, AND THE DIFFERENCE BETWEEN ANATOMIC AND MECHANICAL ALIGNMENT IN KNEES WITH, OR AT RISK OF DEVELOPING OSTEOARTHRITIS D. Wu y, F. Liu z, J.A. Lynch z, X. Li z, B.L. Wise x, N.E. Lane x. yUniv. of California, Berkeley, Berkeley, CA, USA; zUniv. of California, San Francisco, San Francisco, CA, USA; xUniv. of California, Davis, Davis, CA,

Modified osteotomy (Kanaya’s procedure) for congenital proximal radioulnar synostosis with posterior dislocation of radial head

Outcomes of Kanaya's procedure for congenital proximal radioulnar synostosis varied depending on the type of radial head dislocation. In our series of 14 patients with 17 forearms who underwent Kanaya's original procedure, the postoperative total rotation arc of the forearm was unsatisfactory in cases with posterior radial head dislocation. We examined the outcomes with respect to the type of radial head dislocation and radial shaft curvature. Radial shafts with a posterior radial head dislocation had only one curve and the radii of the curve were statistically smaller than those in anterior dislocated or enlocated heads, which had two curves. As a result, we modified the osteotomy site for proximal radioulnar synostosis with posterior radial head dislocation and achieved improved forearm rotation and physiological rotation of the radial head in our latest two cases.

Failure analysis of the repair procedure of an ore compactor roll

This paper deals with the failure analysis of a potassium ore compactor roll that experienced short term fracture in service after a repair procedure. The journal bearing of the shaft experienced wear after a long period in use. Afterwards, a surface deposition was performed in order to retrieve the roll functionality, but it culminated in the formation of radial cracks beginning just near the shaft curvature radius. This portion of the roll was then removed and replaced with a new shaft interference-fitted and welded into the roll. Moreover, after this new repair procedure, the roll experienced a short term fracture. Failure analyses were performed by liquid penetrant, fracture analysis, hardness testing and metallographic analysis. Numerical simulations were also carried out considering the last repair features. Fatigue failure nucleated near a singularity at the shaft curvature radius. This singularity was originated from the interference fit and welding procedures.

Finite element modelling versus classic beam theory: comparing methods for stress estimation in a morphologically diverse sample of vertebrate long bones

Classic beam theory is frequently used in biomechanics to model the stress behaviour of vertebrate long bones, particularly when creating intraspecific scaling models. Although methodologically straightforward, classic beam theory requires complex irregular bones to be approximated as slender beams, and the errors associated with simplifying complex organic structures to such an extent are unknown. Alternative approaches, such as finite element analysis (FEA), while much more time-consuming to perform, require no such assumptions. This study compares the results obtained using classic beam theory with those from FEA to quantify the beam theory errors and to provide recommendations about when a full FEA is essential for reasonable biomechanical predictions. High-resolution computed tomographic scans of eight vertebrate long bones were used to calculate diaphyseal stress owing to various loading regimes. Under compression, FEA values of minimum principal stress (σ(min)) were on average 142 per cent (±28% s.e.) larger than those predicted by beam theory, with deviation between the two models correlated to shaft curvature (two-tailed p = 0.03, r(2) = 0.56). Under bending, FEA values of maximum principal stress (σ(max)) and beam theory values differed on average by 12 per cent (±4% s.e.), with deviation between the models significantly correlated to cross-sectional asymmetry at midshaft (two-tailed p = 0.02, r(2) = 0.62). In torsion, assuming maximum stress values occurred at the location of minimum cortical thickness brought beam theory and FEA values closest in line, and in this case FEA values of τ(torsion) were on average 14 per cent (±5% s.e.) higher than beam theory. Therefore, FEA is the preferred modelling solution when estimates of absolute diaphyseal stress are required, although values calculated by beam theory for bending may be acceptable in some situations.

The correspondence between proximal phalanx morphology and locomotion: Implications for inferring the locomotor behavior of fossil catarrhines

Phalanges are considered to be highly informative in the reconstruction of extinct primate locomotor behavior since these skeletal elements directly interact with the substrate during locomotion. Variation in shaft curvature and relative phalangeal length has been linked to differences in the degree of suspension and overall arboreal locomotor activities. Building on previous work, this study investigated these two skeletal characters in a comparative context to analyze function, while taking evolutionary relationships into account. This study examined the correspondence between proportions of suspension and overall substrate usage observed in 17 extant taxa and included angle of curvature and relative phalangeal length. Predictive models based on these traits are reported. Published proportions of different locomotor behaviors were regressed against each phalangeal measurement and a size proxy. The relationship between each behavior and skeletal trait was investigated using ordinary least-squares, phylogenetic generalized least-squares (pGLS), and two pGLS transformation methods to determine the model of best-fit. Phalangeal curvature and relative length had significant positive relationships with both suspension and overall arboreal locomotion. Cross-validation analyses demonstrated that relative length and curvature provide accurate predictions of relative suspensory behavior and substrate usage in a range of extant species when used together in predictive models. These regression equations provide a refined method to assess the amount of suspensory and overall arboreal locomotion characterizing species in the catarrhine fossil record.

Identification of a multi-crack in a shaft system using transverse frequency response functions

The identification of multiple cracks in a shaft is still a real challenge. In the present work, a two-stage identification methodology has been developed, which identifies a number of cracks, their locations on a cracked shaft and its sizes. The methodology uses transverse forced responses of the shaft system at different frequencies of a harmonic excitation. In the first stage, a multi-crack detection and its localization algorithm are developed. Transverse forced vibrations of a non-rotating cracked shaft in two orthogonal planes are analyzed with the help of the finite element method by using the Timoshenko beam theory. The presence of a crack in a shaft introduces a slope discontinuity in the elastic line of the shaft. This causes a jump in the value of the curvature of the shaft elastic line, and it is difficult to measure in the presence of measurement noise. In the present work, the shaft curvature is obtained by approximating forced responses of the shaft at consecutive axial measurement locations by a polynomial. The effect of noise is reduced by utilizing forced responses of the shaft at several frequencies. This stage of the algorithm gives the number of cracks and their approximate locations over the shaft. In the second stage of the algorithm, the size and the accurate location of cracks are obtained by using multi-objective genetic algorithms. Responses of the shaft at several frequencies are used to define objective functions in GA. The proposed two-stage methodology is tested with numerically simulated noisy forced responses from the finite element modeling of a simply supported shaft having two cracks. The methodology identifies very well the presence of cracks and also estimates quite accurately the location and the size of cracks on the shaft.

Simultaneous Measurement of Torsion and Curvature Using Curvature Fiber Optic Sensor

Curvature fiber optic sensors are a kind of novel low cost sensors that can detect curvature directly and distinguish the positive bending and negative bending. This kind of sensor is used to detect torsion deformation of shaft in this paper. The optimal direction of curvature fiber optic sensor was analyzed in osculating plane and rectification plane and maximal sensitivity was gained. The results show that sensor response to the torsion angle is linear approximately. Torsion angle, curvature and bending direction of shaft were measured simultaneously by using curvature fiber optic sensors.