Total Contact Area Research Articles

Reliability of the special support system for sitting pressure redistribution.

[Purpose] This study investigated the reliability of the Special Support System. [Subjects and Methods] Eighteen female and 14 male volunteers participated in this study. Participants were asked to sit on the Special Support System with their chins tucked in, spines straight, pelvis neutrally positioned, and their hands placed on their thighs. They were also asked to flex their hips, knees, and ankles to approximately 90 degrees and to put their feet flat on the floor. The total contact area, mean total pressure, as well as mean and peak pressures of each quadrant were each measured 15 times. Test-retest reliability was analyzed for inflated air pressure, and pressure redistribution values by using intraclass correlation coefficients. [Results] The intraclass correlation coefficient was greater than 0.89 for inflated air pressure and greater than 0.92 for total contact area, mean total pressure, and each quadrant’s mean and peak pressure. [Conclusion] The findings suggest that the Special Support System is reliable and can be used as an alternative method for redistributing sitting pressure.

Botulinum Toxin Type A Injection for Spastic Equinovarus Foot in Children with Spastic Cerebral Palsy: Effects on Gait and Foot Pressure Distribution.

PurposeTo investigate the effect of intramuscular Botulinum toxin type A (BoNT-A) injection on gait and dynamic foot pressure distribution in children with spastic cerebral palsy (CP) with dynamic equinovarus foot.Materials and MethodsTwenty-five legs of 25 children with CP were investigated in this study. BoNT-A was injected into the gastrocnemius (GCM) and tibialis posterior (TP) muscles under the guidance of ultrasonography. The effects of the toxin were clinically assessed using the modified Ashworth scale (MAS) and modified Tardieu scale (MTS), and a computerized gait analysis and dynamic foot pressure measurements using the F-scan system were also performed before injection and at 1 and 4 months after injection.ResultsSpasticity of the ankle plantar-flexor in both the MAS and MTS was significantly reduced at both 1 and 4 months after injection. On dynamic foot pressure measurements, the center of pressure index and coronal index, which represent the asymmetrical weight-bearing of the medial and lateral columns of the foot, significantly improved at both 1 and 4 months after injection. The dynamic foot pressure index, total contact area, contact length and hind foot contact width all increased at 1 month after injection, suggesting better heel contact. Ankle kinematic data were significantly improved at both 1 and 4 months after injection, and ankle power generation was significantly increased at 4 months after injection compared to baseline data.ConclusionUsing a computerized gait analysis and foot scan, this study revealed significant benefits of BoNT-A injection into the GCM and TP muscles for dynamic equinovarus foot in children with spastic CP.

Heat-Integrated Liquid–Desorption Exchanger (HILDE) for CO2 Desorption

A novel type of separating heat exchanger, called a heat-integrated liquid−desorption exchanger (HILDE), applied to a typical CO2 desorption process, has been investigated both numerically and experimentally. Process simulations, hydrodynamic and mass transfer experiments, and a preliminary cost evaluation have been used to compare HILDE to the conventionally used combination of a separate heat exchanger and desorber equipped with structured packing.The comparison revealed that the operational costs of the HILDE are 15% lower compared to the conventional desorption configuration, while the equipment costs are 45% lower. The reduction in operational costs is mainly caused by a reduced reboiler duty. The absence of a separate desorber column and a large decrease in the condenser size are the main reasons for the reduced equipment costs. Additionally, the system volume, mass hold-up, and total contact area are also expected to be significantly lower for HILDE.

How Do Hindfoot Fusions Affect Ankle Biomechanics: A Cadaver Model

While successful subtalar joint arthrodesis provides pain relief, resultant alterations in ankle biomechanics need to be considered, as this procedure may predispose the remaining hindfoot and tibiotalar joint to accelerated degenerative changes. However, the biomechanical consequences of isolated subtalar joint arthrodesis and additive fusions of the Chopart's joints on tibiotalar joint biomechanics remain poorly understood. We asked: What is the effect of isolated subtalar fusion and sequential Chopart's joint fusions of the talonavicular and calcaneocuboid joints on tibiotalar joint (1) mechanics and (2) kinematics during loading for neutral, inverted, and everted orientations of the foot? We evaluated the total force, contact area, and the magnitude and distribution of the contact stress on the articular surface of the talar dome, while simultaneously tracking the position of the talus relative to the tibia during loading in seven fresh-frozen cadaver feet. Each foot was loaded in the unfused, intact control condition followed by three randomized simulated hindfoot arthrodesis modalities: subtalar, double (subtalar and talonavicular), and triple (subtalar, talonavicular, and calcaneocuboid) arthrodesis. The intact and arthrodesis conditions were tested in three alignments using a metallic wedge insert: neutral (flat), 10° inverted, and 10° everted. Tibiotalar mechanics (total force and contact area) and kinematics (external rotation) differed owing to hindfoot arthrodeses. After subtalar arthrodesis, there were decreases in total force (445 ± 142 N, 95% CI, 340-550 N, versus 588 ± 118 N, 95% CI, 500-676 N; p < 0.001) and contact area (282 mm(2), 95% CI, 222-342 mm(2), versus 336 ± 96 mm(2), 95% CI, 265-407 mm(2); p < 0.026) detected during loading in the neutral position; these changes also were seen in the everted foot position. Hindfoot arthrodesis also was associated with increased external rotation of the tibiotalar joint during loading: subtalar arthrodesis in the neutral loading position (3.3° ± 1.6°; 95% CI, 2°-4.6°; p = 0.004) and everted loading position (4.8° ± 2.6°; 95% CI, 2.7°-6.8°; p = 0.043); double arthrodesis in neutral (4.4° ± 2°; 95% CI, 2.8°-6°; p = 0.003) and inverted positions (5.8° ± 2.6°; 95% CI, 3.7°-7.9°; p = 0.002), and triple arthrodesis in all loaded orientations including neutral (4.5° ± 1.8°; 95% CI, 3.1°-5.9°; p = 0.002), inverted (6.4° ± 3.5°; 95% CI, 3.6°-9.2°; p = 0.009), and everted (3.6° ± 2°; 95% CI, 2°-5.2°; p = 0.053) positions. Finally, after subtalar arthrodesis, additive fusions at Chopart's joints did not appear to result in additional observed differences in tibiotalar contact mechanics or kinematics with the number of specimens available. Using a cadaveric biomechanical model, we identified some predictable trends in ankle biomechanics during loading after hindfoot fusion. In our tested specimens, fusion of the subtalar joint appeared to exert a dominant influence over ankle loading. A loss or deficit in function of the subtalar joint may be sufficient to alter ankle loading. These findings warrant consideration in the treatment of the arthritic hindfoot and also toward defining biomechanical goals for ankle arthroplasty in the setting of concomitant hindfoot degeneration or arthrodesis.

Droplet freezing and ice adhesion strength measurement on super-cooled hydrophobic surfaces

ABSTRACTThis report investigates the freezing of water droplets on hydrophobic surfaces and reports a means to quantitatively measure the ice-adhesion strength at micro-patterned hydrophobic surfaces. Water droplets were placed on a super-cooled surface where they froze following the heterogeneous nucleation phase-transition. The freezing occurred with two distinct transitions: (a) an initial snapping transition freezing of the external shell of the droplet, and (b) a subsequent bulk freezing of the droplet with a characteristic formation of peaked apex protruding upwardly. To measure the ice-adhesion strength, frozen droplets were sheared from the surface using a Universal Materials Tester (UMT) measuring the resulting knock-off forces. Ice formation and adhesion was investigated on three variations of hydrophobic polydimethylsiloxane (PDMS) surfaces: regularly patterned with high and low surface densities of micro-pillar arrays and non-patterned flat surfaces. Patterning the surfaces was found to accelerate freezing transitions but decrease the measured ice-adhesion strength in correlation with a reduction of total interfacial contact area. However, a more concentrated local stress was observed for the less dense surface structures, indicating a potential area of concern for more fragile systems.

Geometric Effect of Asperities on Shear Mechanism of Rock Joints

Three-dimensional tracking of changes of asperities is one of the most important ways to illustrate shear mechanism of rock joints during testing. In this paper, the changes of the role of asperities during different stages of shearing are described by using a new methodology for the characterization of the asperities. The basis of the proposed method is the examination of the three-dimensional roughness of joint surfaces scanned before and after shear testing. By defining a concept named ‘tiny window’, the geometric model of the joint surfaces is reconstructed. Tiny windows are expressed as a function of the x and y coordinates, the height (z coordinate), and the angle of a small area of the surface. Constant normal load (CNL) direct shear tests were conducted on replica joints and, by using the proposed method, the distribution and size of contact and damaged areas were identified. Image analysis of the surfaces was used to verify the results of the proposed method. The results indicated that the proposed method is suitable for determining the size and distribution of the contact and damaged areas at any shearing stage. The geometric properties of the tiny windows in the pre-peak, peak, post-peak softening, and residual shearing stages were investigated based on their angle and height. It was found that tiny windows that face the shear direction, especially the steepest ones, have a primary role in shearing. However, due to degradation of asperities at higher normal stresses and shear displacements, some of the tiny windows that do not initially face the shear direction also come in contact. It was also observed that tiny windows with different heights participate in the shearing process, not just the highest ones. Total contact area of the joint surfaces was considered as summation of just-in-contact areas and damaged areas. The results of the proposed method indicated that considering differences between just-in-contact areas and damaged areas provide useful insights into understanding the shear mechanism of rock joints.

Thermal Conductance of Cu and Carbon Nanotube Interface Enhanced by a Graphene Layer**Supported by the National Science Foundation of China under Grant No 61131004, and the Fundamental Research Funds for the Central Universities under Grant No DUT14LAB11.

Thermal conductances between Cu and graphene covered carbon nanotubes (gCNTs) are calculated by molecular dynamics simulations. The results show that the thermal conductance is about ten times larger than that of Cu-CNT interface. The enhanced thermal conductance is due to the larger contact area introduced by the graphene layer and the stronger thermal transfer ability of the Cu-gCNT interface. From the linear increasing thermal conductance with the increasing total contact area, an effective contact area of such an interface can be defined.

Definition and detection of contact in atomistic simulations

In atomistic simulations, contact depends on the accurate detection of contacting atoms as well as their contact area. While it is common to define contact between atoms based on the so-called ‘contact distance’ where the interatomic potential energy reaches its minimum, this discounts, for example, temperature effects on atomic vibrations and, correspondingly, the spatial distributions of atoms. In the present study, classical molecular dynamics was used to investigate the definition and detection of contact between a spherical particle (made of either silver, lead, or platinum) and a flat substrate (silver). Total contact areas are estimated via three previously published methods for the detection of atoms in contact: the first method detects contacting atoms based on their potential energy values; the second method utilizes interatomic distances; and, the last method is based on the interacting potential energy values between the contacting atoms of the counterpart surfaces. Each method is examined in detail with our findings suggesting that the use of interatomic distances is the most suitable way to define and detect the real area of contact in atomistic simulations of normal contact. Our results suggest that the minimum of the radial distribution function after the first peak can be defined as the contact distance. Also, a temperature-dependent empirical equation is proposed to estimate the contact distance for Lennard-Jones-type potentials. Moreover, the atomic diameter is defined as the distance between the origin (i.e. the center of the reference atom) and the first peak in the radial distribution function, allowing for an estimation of the atomic contact area.

Use of custom insoles for redistributing plantar pressure, decreasing musculoskeletal pain and reducing postural changes in obese adults

Introduction Insoles are used for different purposes and they can be an additional factor aiding weight loss in obese people due to their contribution in reducing musculoskeletal pain. Objective The aim of the present study was to assess the effect of custom insoles for redistributing plantar pressure, decreasing musculoskeletal pain and reducing postural changes in obese adults. Materials and methods Data was obtained from morbidly obese people, who had a Body Mass Index (BMI) ≥ 35 and &lt; 45 kg/m2, at three moments: before the insole was provided, immediately after insole use began and after two months of use. Anthropometric, postural, musculoskeletal pain and computerized baropodometry data were collected. Results When comparing the stages before the use of the insole and after two months of use, significant (p &lt; 0.05) decreases were observed in the number of people with right lateral postural misalignment, in the intensity of the musculoskeletal pain of the body segments evaluated (except for the right knee), and in the mean of the peak plantar pressure values. In terms of total plantar contact area, the mean increased significantly (p &lt; 0.05) in both right and left feet after the intervention. Conclusion This study demonstrated that the daily use of proprioceptive insoles contributed to reducing peak plantar pressure, musculoskeletal pain and lateral postural deviations. The use of proprioceptive insoles may be an important strategy to encourage obese people to exercise and, consequently, reduce weight.

Interactions of microorganisms with polymer nanocomposite surfaces containing oxidized carbon nanotubes.

In many environmental scenarios, the fate and impact of polymer nanocomposites (PNCs) that contain carbon nanotubes (CNT/PNCs) will be influenced by their interactions with microorganisms, with implications for antimicrobial properties and the long-term persistence of PNCs. Using oxidized single-wall (O-SWCNTs) and multi-wall CNTs (O-MWCNTs), we explored the influence that CNT loading (mass fraction≤0.1%-10%) and type have on the initial interactions of Pseudomonas aeruginosa with O-CNT/poly(vinyl alcohol) (PVOH) nanocomposites containing well-dispersed O-CNTs. LIVE/DEAD staining revealed that, despite oxidation, the inclusion of O-SWCNTs or O-MWCNTs caused PNC surfaces to exhibit antimicrobial properties. The fraction of living cells deposited on both O-SWCNT and O-MWCNT/PNC surfaces decreased exponentially with increasing CNT loading, with O-SWCNTs being approximately three times more cytotoxic on a % w/w basis. Although not every contact event between attached microorganisms and CNTs led to cell death, the cytotoxicity of the CNT/PNC surfaces scaled with the total contact area that existed between the microorganisms and CNTs. However, because the antimicrobial properties of CNT/PNC surfaces require direct CNT-microbe contact, dead cells were able to shield living cells from the cytotoxic effects of CNTs, allowing biofilm formation to occur on CNT/PNCs exposed to Pseudomonas aeruginosa for longer time periods.

Effects of Acetabular Rim Trimming on Hip Joint Contact Pressure

Objectives:In patients with femoroacetabular impingement (FAI), acetabular rim trimming removes the offending cause of pain in patients with pincer-type and mixed-pincer-cam type pathology and helps protect repaired damaged labrum from further injury. Although the clinical benefit of arthroscopic acetabular rim trimming in FAI patients is well established, the threshold at which excessive rim resection results in abnormal hip contact pressures from iatrogenic acetabular dysplasia has never been studied. The purpose of the present study was to investigate the changes in contact areas, contact pressures and peak forces within the hip joint with sequential acetabular rim-trimming.Methods:A comparative biomechanical analysis of 4 fresh-frozen human cadaver hemi-pelvises was performed. Prior to testing, all specimens underwent a CT scan and were deemed non-dysplastic based on center edge angle measurements. For each specimen, the acetabulum and proximal femur were potted in dental cement and mounted on a materials testing system (MTS Insight 5, Eden Prairie, MN). After resecting the labrum, a contact pressure and area mapping system (Tekscan, Boston MA) was placed within the acetabulum and a 700 N load was subsequently applied resulting in a real-time pressure map. Each specimen was sequentially tested in the intact state as well as anterosuperior acetabular rim-trimming (from the 12 o’clock to 3 o’clock position) of 2mm, 4mm, 6mm and 8mm depth. Each testing condition was examined at two different positions within the natural hip range of motion: 20° extension and 60° flexion. Analysis of total force, contact area, contact pressure and peak force was performed on two regions of interest: the acetabular rim and the acetabular base (deep part of acetabulum). The rim-trimmed states were then normalized with respect to the intact state in order to help account for specimen variability. Statistical analysis was conducted via a Paired and Unpaired Student’s T-test on normalized data.Results:At 60° flexion, rim-trim depth was significantly correlated to acetabular rim contact area (R=-0.698, P=0.001), contact pressure (R=-0.892, P<0.001) and peak force (R=-0.857, P<0.001). At 20° extension, rim-trim depth was significantly correlated to acetabular rim contact area (R=-0.684, P=0.001), contact pressure (R=-0.673, P=0.001) and peak force (R=-0.574, P=0.008). With regards to the acetabular base, at 60° flexion and 6mm resection there was a statistically significant increase in both base contact pressure (393.90%±163.33, P=0.020) and base peak force (178.94%±75.7, P=0.026). There was also a significant increase in base contact area after 8mm resection at 60° flexion (408.15%±224.17, P=0.015). At 60° flexion, rim-trim depth was significantly correlated to acetabular base contact area (R=0.604, P=0.005), contact pressure (R=0.718, P<0.001) and peek force (R=0.593, P=0.006).Conclusion:Resecting more than 4-6 mm of bone in an acetabular rim trimming hip arthroscopy procedure may dramatically increase hip joint contact pressures and predispose patients to early osteoarthritis via creation of an iatrogenic acetabular dysplasia. In dysplastic or borderline dysplastic hips, the amount of safe resection may be even less.

The 3D nature of a real un-dismantled electrical contact interface

A 3D contact analysis and modeling suite of tools are developed and introduced in this work. The “3D Contact Map” of an electrical contact interface is presented demonstrating the 3D nature of the contact. It gives information on where the electrical contact spots in a 3D surface profile are located. An X-ray Computer Tomography (CT) technique is used to collect the 3D data to a resolution of around 5μm of a real un-dismantled contact interface for analysis. Previous work by Lalechos and Swingler presented “2D Contact Map” on a 2D contact profile from collected 3D data to a resolution of around 8μm. The main advantages of both 3D and 2D mapping techniques focus on the fact that they are non-destructive and there is no need to dismantle the component of interest. This current work focuses on the 3D mapping technique showing its advantages over the 2D mapping technique. For test purposes, a 16A rated AC single pole switch is scanned after two different current loading tests (0A and 16A). A comparison for the total mechanical area of contact, the number of contact spots and the total contact resistance is conducted using both the 2D and 3D mapping techniques to a resolution of around 5μm.

Biomechanical properties of labral repair: simple versus vertical suture pattern.

The goal of this study was to evaluate contact area and surface pressure as a result of different suture patterns in the treatment of anterior shoulder instability caused by a Bankart lesion. Loads were applied through the humeral head to the glenoid surface in the intact shoulder and after simple suture labral repair (n=10) and vertical mattress labral repair (n=9). Peak contact pressure, mean contact pressure, and contact area were recorded for 0°, 45°, and 90° shoulder abduction, and then the repair was loaded to failure. A significant increase (P<.05) in mean contact pressure and peak contact pressure occurred in both repair groups at 90° abduction. No difference was seen between the 2 repair groups. Total contact area significantly decreased after both repairs at 90° abduction at 220 N force (P<.05). No significant difference occurred in load to failure between the groups. Joint loading properties can be affected by alterations in contact pressure within the glenohumeral joint. In the current study, the authors found no significant difference in contact pressure between the 2 repair groups. However, they found a significant increase in mean contact pressure and peak pressure between the intact specimen and the 2 repair groups. Both simple repair and vertical mattress repair provided similar load to failure for labral repair. Current techniques used to perform Bankart repair may need to be altered to provide the stability of current techniques with more normal glenohumeral joint contact pressure.

Numerical Simulations of Gravity Driven Reversible Reactive Flows in Homogeneous Porous Media

The effect of reversibility on the instability of a miscible vertical reactive flow displacement is examined. A model, where densities and/or viscosities mismatches between the reactants and the chemical product trigger instability, is adopted. The problem is governed by the continuity equation, Darcy’s law, and the convection-diffusion-reaction equations. The problem is formulated and solved numerically using a combination of the highly accurate spectral methods based on Hartley’s transform and the finite-difference technique. Nonlinear simulations were carried out for a variety of parameters to analyse the effects of the reversibility of the chemical reaction on the development of the flow under different scenarios of the frontal instability. In general, faster attenuation in the development and growth of the instability is reported as the reversibility of the chemical reaction increases. However, it was observed that reversibility is capable of triggering instability for particular choices of the densities and viscosities mismatches. In addition, the effect of the reversibility in enhancing the instability was illustrated by presenting the total relative contact area between the reactants and the product.

Glycogen and amyloid-beta: key players in the shift from neuronal hyperactivity to hypoactivity observed in Alzheimer′s disease?

Glycogen and amyloid-beta: key players in the shift from neuronal hyperactivity to hypoactivity observed in Alzheimer′s disease?

Comparison of direct and indirect occlusal contact examinations with different clenching intensities.

The aims of this study were to examine the change of occlusal contact area following the increment of clenching intensity using silicone materials and electromyography (EMG) in normal subjects and to compare direct intra-oral examination with indirect examination using dental casts mounted by means of two impression methods. Participants were 7 men and 5 women with no more than one missing tooth per quadrant and no pain in the head and neck region. During the task, intercuspal position was maintained with minimal force, 20% maximum voluntary contraction (MVC) and 40% MVC using electromyography visual feedback. Three types of occlusal contact examinations were performed with the aid of blue silicone material in randomised order: (i) intra-oral direct occlusal contact examination (DE), (ii) indirect occlusal contact examination with dental casts using conventional impression method (IEC) and (iii) using occlusal impression method (IEO). Total occlusal contact area during DE and IEO significantly increased from baseline to 20% MVC and from baseline to 40% MVC, but not during IEC. Total occlusal contact area during DE in all tooth clenching conditions was significantly larger compared to IEO and IEC (P<0·05). At 40% MVC, total occlusal contact area during IEO was significantly larger than during IEC (P<0·05). These findings suggest that indirect occlusal contact examinations may not accurately reflect the intra-oral occlusal condition. If the intra-oral condition is reproduced using dental casts, these findings also suggest the occlusal impression method was more accurate compared to the conventional method (240 words).

Nano-Halloysite Concentration Effects on Fracture Toughness of Diverse Epoxy Nanocomposites

Abstract We experimentally report material design of halloysite nanotube (HNT)/epoxy composites, focusing on the effects of HNT concentration on thermal and mechanical properties, especially fracture toughness, of diverse epoxy composites with as-received and phenylphosphonic-acid (PPA)-treated HNTs prepared by mechanical mixing or ball-milling homogenization. It is demonstrated that, with HNT added in the region of 0.0–10.0 wt. %, significantly reinforced fracture toughness of the epoxy composites can be achieved. The epoxy composites prepared by ball-milling homogenization have much more uniform HNT size and dispersion than those prepared by simple mechanical mixing, enhancing their fracture toughness. The morphology of treated HNTs changes from nanotubes to nanoplatelets; as a result, with a substantial increase in the total contact area between HNT and epoxy and enhancing the fracture toughness of epoxy composites. This higher HNT concentration and the higher fracture toughness are achieved for various epoxy composites. However, the optimal concentration of HNT is 5.0 wt. % in this study. The addition of further HNT achieves only marginal fracture toughness enhancement and more negative effects appear, such as HNT concentration gradient in cured epoxy composites, high potential decrease in glass transition temperature (Tg), and potential immature tensile failure.

In vitro assessment of the contact mechanics of reverse-engineered distal humeral hemiarthroplasty prostheses

BackgroundDistal humeral hemiarthroplasty alters cartilage contact mechanics, which may predispose to osteoarthritis. Current prostheses do not replicate the native anatomy, and therefore contribute to these changes. We hypothesized that prostheses reverse-engineered from the native bone shape would provide similar contact patterns as the native articulation. MethodsReverse-engineered hemiarthroplasty prostheses were manufactured for five cadaveric elbows based on CT images of the distal humerus. Passive flexion trials with constant muscle forces were performed with the native articulation intact while bone motions were recorded using a motion tracking system. Motion trials were then repeated after the distal humerus was replaced with a corresponding reverse-engineered prosthesis. Contact areas and patterns were reconstructed using computer models created from CT scan images combined with the motion tracker data. The total contact areas, as well as the contact area within smaller sub-regions of the ulna and radius, were analyzed for changes resulting from hemiarthroplasty using repeated-measures ANOVAs. FindingsContact area at the ulna and radius decreased on average 42% (SD 19%, P=.008) and 41% (SD 42%, P=.096), respectively. Contact area decreases were not uniform throughout the different sub-regions, suggesting that contact patterns were also altered. InterpretationReverse-engineered prostheses did not reproduce the same contact pattern as the native joints, possibly because the thickness of the distal humerus cartilage layer was neglected when generating the prosthesis shapes or as a consequence of the increased stiffness of the metallic implants. Alternative design strategies and materials for hemiarthroplasty should be considered in future work.

Effects of the insert to plantar contact area and pressure distribution

The purpose of this study is to investigate the effects of inserts that are used for conservative treatment of excessive foot pronation, on plantar contact areas and pressure distribution. 27 subjects consisting of 6 men and 21 women, mean age 25.88±5.92, and having excessive foot pronation were included in this study. Demographic data were recorded. Short Form McGill Questionnaire, Navicular Drop Test, Foot Posture Index and Foot Function Index were performed for each subject. Subjects were evaluated with dynamic pedobarography (Rs Scan-Footscan ®), first barefoot, than with spesific inserts, to assess plantar contact area and pressure distribution. Findings from dynamic pedobarography indicated that there were significant increase at total contact area, contact area percents of midfoot, significant decrease at contact area percents of fore and rearfoot, at maximum plantar pressures on 2., 3., 4. metatars areas of left foot and on 2. and 3. metatars areas of right foot, on medial and lateral heel with insert according to barefoot (p=0.007, p=0.001, p=0.003, p 0,05). Excessive foot pronation, causes pathologic changes on proximal and distal subtalar joint, effects plantar pressures destroying load distribution. Using insert is the most common method to correct this deformity. The results of our study emphasizes, spesific inserts are effective to distribute plantar pressures and prevent excessive loading of specific areas increasing contact area.

The impact of fibre surface morphology on the effective thermal conductivity of a polymer electrolyte membrane fuel cell gas diffusion layer

In this work, the effect of fibre surface morphology on the effective thermal conductivity of the gas diffusion layer of a polymer electrolyte membrane fuel cell is presented. Atomic force microscopy was used to measure the fibre surface roughness and asperity height distributions for various fibres for Toray carbon paper. Hertzian contact mechanics was used to determine individual micro-contact areas and thermal resistances, and results were compared with the smooth cylinder approximation. The effective thermal contact resistance between rough fibres was determined using resistance network theory. The thermal contact resistance and total contact area were determined for various angles of fibre orientation and contact forces; results are presented as empirical formulations. It was found that the effective thermal contact resistance is significantly affected by fibre roughness features when compared to the smooth fibre case, which is often used in the literature. The analysis conducted provides an alternative to computationally expensive surface feature analyses by providing a tool which can be used to implement the nano-scale features of gas diffusion layer fibres into existing effective thermal conductivity models.